HOUSEHOLD 


CHEMISTRY 


BY 


H.  T,  VULTE  and   G.  A,  GOODELL 


STATT 

LOF 


CALIFORNIA 


i  ;-:xGELES 
LIBRARY 


LABORATORY  NOTES 

IN 

HOUSEHOLD  CHEMISTRY 

FOR  THE  USE  OF 

STUDENTS  IN  DOMESTIC  SCIENCE 

BY 
HERMANN  T.  VULTE,  Ph.D.,  F.C.S., 

Assistant  Professor  in  Household  Chemistry  in 
Teachers  College,  Columbia  University, 

^  30  /  5~ 
AND 

GEORGE  A.  GOODELL,  A.B.,  A.M., 

Instructor  in  Chemistry,  Wellesley  College 


THIRD    EDITION 


EASTON,   PA.: 

THE  CHEMICAL  PUBLISHING  COMPANY 
1911 


8,3015 


COPYRIGHT,  1904,  BY  H.  T.  VULTE 
COPYRIGHT,  1910,  BY  H.  T.  VULTE 
COPYRIGHT,  1911,  BY  H.  T.  VULTE 


TX 

\*\ 

V  s>" 


Preface  to  the  Third  Edition 


In  consequence  of  the  rapid  exhaustion  of  the  second 
edition,  it  has  become  necessary  to  issue  the  present  third 
Edition  which  has  been  thoroughly  revised  and  corrected. 

June,  1911. 


Table  of  Contents 


Introduction. — Construction  of  the  Bunsen  Burner.  Instruction 
for  Manipulating  Glass  Tubing  and  Constructing  Simple  Appa- 
ratus. Construction  and  Use  of  the  Wash-Bottle.  Page  i 

PART  I 

Chapter  I. — Fuels :  Solids ;  liquids ;  gases.  Scheme  for  the 
Separation  and  Detection  of  Acid  Ions  CO3,  PO4,  SO*  and  Cl  and 
Basic  Ions  Ca,  Mg,  NH<,  Na  and  K.  Page  6 

Chapter  II. — Carbon  Dioxide.  Composition.  Properties.  Prep- 
aration of  Bicarbonate  of  Lime.  Formation  of  Sodium  Bicar- 
bonate. Page  31 

Chapter  III. — Atmosphere.  Composition.  Special  Functions 
of  Constituents  with  Regard  to  Plant  and  Animal  Organisms. 

Page  34 

Chapter  IV. — Water.  Physical  and  Chemical  Properties.  Classi- 
fication. As  a  Solvent.  Distillation.  Qualitative  Examination. 

Page  38 

Chapter  V. — Metals  and  Alloys.  Processes  of  Manufacture. 
Physical  and  Chemical  Properties.  Effect  of  Acids  and  Alka- 
lies. Methods  of  Cleaning.  Page  52 

Chapter  VI. — Acids  and  Bases.  Properties.  Normal  Solutions. 

Page  71 

Chapter  VII.— Glass.    Pottery.     Porcelain.  Page  85 

Chapter  VIIL— Paints.    Varnishes.  Page  91 

PART  II 

Chapter  IX. — Food  Principles.  Carbohydrates.  Starch.  Dex- 
trines.  Glycogen.  Celluloses.  Glucoses.  Sucrose.  Maltose. 
Lactose.  Page  96 


CONTENTS  V 

Chapter  X. — Methods  for  Testing  Flour.  Meals.  Raw  and 
Cooked  Potatoes.  Bread.  Toast.  Cereals.  Page  122 

Chapter  XL — Fats  and  Oils.  Composition.  Properties.  Ex- 
traction from  Animal  and  Vegetable  Sources.  Drying  Oils.  Prep- 
aration of  Soap.  Butter.  Page  128 

Chapter  XII. — Protein  Bodies.  Composition.  Properties.  Al- 
bumens and  Globulins.  Yolk  of  Egg.  Gelatine.  Bones.  Muscle. 

Page  138 

Chapter  XIII. — Milk.  Composition.  Properties.  Physical  and 
Chemical  Tests.  Quantitative  Analysis.  Effect  of  Rennet.  Cheese. 
Composition.  Page  154 

Chapter  XIV. — Ferments  and  Preservatives.  Yeast.  Acetous 
Fermentation.  Lactic  Acid.  Food  Preservation.  Methods  for 
Detecting  Preservatives.  Page  164 

Chapter  XV. — Baking  Powders.  Composition.  Determination 
of  CO*  Page  172 

Chapter  XVI.— Tea.  Coffee.  Chocolate.  Cocoa.  Methods  of 
Preparation.  Experiments.  Page  178 

Chapter  XVII.— Stains.    Methods  of  Removing.         Page  182 

Chapter  XVIIL— Reagents.  Methods  of  Preparation.     Page  186 


Introduction 


CONSTRUCTION  OF  THE  BUNSEN  BURNER 

2  3  O  I S 

Unscrew  the  tube,  examine  and  light  the  inner  jet. 
Examine  the  outer  tube  and  collar  that  controls  the 
air-ports.  Turn  off  the  gas  and  replace  the  tube.  Now 
turn  on  the  gas  again,  strike  a  match  and  approach 
it  to  the  top  of  the  tube.  Always  observe  this  latter 
precaution  when  lighting  the  Bunsen  burner.  Observe 
the  character  and  color  of  the  flame,  move  the  collar 
on  the  tube  and  note  the  effect.  Hold  a  piece  of  glass 
tubing  near  the  top  of  the  flame,  remove  from  the 

^P  flame  and  bend.     Hold  it  in  the  same  position  in  the 

'   yellow  flame,  and  after  removal  observe  the  condition 

of  the  tube  and  try  to  bend  it.     Is  there  any  apparent 

difference  in  the  intensity  of  the  heat  developed?   Lower 

•'o  a  piece  of  fine  iron  wire  gauze  half  way  in  the  flame, 
why  does  the  flame  fail  to  penetrate  the  gauze?  Apply 
a  light  above  the  gauze,  explain  the  phenomenon.  Place 
a  piece  of  paper  on  the  gauze,  lower  it  half  way  in  the 
flame,  notice  the  charred  ring.  Hold  a  splinter  at  the 
same  point  in  the  flame,  note  where  it  is  charred  and 
explain.  Introduce  the  large  end  of  a  dropping  tube 


2  HOUSEHOLD    CHEMISTRY 

into  the  flame  near  the  tube,  and  approach  a  light  near 
the  exit.  From  the  results  of  the  last  three  experiments 
what  is  your  idea  of  the  combustion  zone? 

Carefully  turn  the  gas  down  at  the  key,  watch  the 
effect,  why  does  the  flame  disappear?  Now  immediately 
turn  the  gas  on  full  force  and  note  the  result.  Approach 
a  light  to  the  upper  end  of  the  tube,  observe  the  char- 
acter of  the  flame,  compare  v/ith  the  original  flame  as 
to  color  and  heating  effect.  Strike  the  rubber  tube  a 
quick  blow  with  the  closed  hand  and  explain  the  result- 
ing phenomenon. 

Make  a  simple  drawing  illustrating  the  structure  of 
the  Bunsen  burner,  with  the  gas  and  air  supply  and 
the  zones  of  combustion  of  the  flame. 

INSTRUCTIONS  FOR  MANIPULATING  GLASS  TUBING 
AND   CONSTRUCTING   SIMPLE   APPARATUS 

Two  kinds  of  glass,  "hard"  and  "soft,"  are  used  in 
making  apparatus  for  the  laboratory.  Hard  glass  is 
very  brittle  and  quite  infusible  in  the  ordinary  Bunsen 
flame.  It  is  used  in  heavy  apparatus  where  a  high 
temperature  is  required  for  heating  dry,  but  never  liquid 
substances,  as  the  latter  would  cause  it  to  break.  It 
can  usually  be  recognized  by  the  striations  on  its  sur- 
face and  by  its  greenish  vellow  color,  best  seen  at  the 
end  of  a  broken  tube. 

Soft  glass  is  less  brittle  than  hard.    It  is  easily  fusible 


MANIPULATING  GLASS  TUBING,  ETC.  3 

in  the  Bunsen  flame  and  is  used  in  the  construction  of 
thin  apparatus  (such  as  beakers,  test-tubes,  etc.,)  for 
heating  liquid,  but  never  dry  substances. 

The  tubing  used  by  the  student  for  bending,  blowing 
and  fitting  up  apparatus  should  be  of  soft  glass. 

Cutting  the  Tube. — Glass  tubing  up  to  one-fourth  inch 
in  diameter  may  readily  be  cut  by  making  a  slight  scratch 
with  a  triangular  file  at  the  point  of  the  fracture,  the 
tube  is  now  grasped  firmly  in  both  hands  holding  the 
scratch  outward  and  the  thumb  nails  pressed  against 
the  inner  side  of  the  tube  opposite  the  mark,  give  a 
slight  bend  outward,  at  the  same  time  pulling  apart ;  the 
tube  will  make  a  clean  break  and  no  injury  will  be  re- 
ceived. Broken  in  this  way  the  tube  ends  are  sharp  and 
should  always  be  rounded  by  heating  for  a  moment  in 
the  flame. 

Bending  the  Tube.— Take  care  that  the  tube  is  perfect- 
ly clean  and  dry  inside  and  outside  before  heating.  Ad- 
just the  wing-top  to  the  burner  and  after  lighting,  heat 
the  tube  lengthwise  in  the  upper  part  of  the  flame.  Re- 
volve the  tube  so  as  to  heat  all  parts  equally ;  when  soft, 
remove  from  the  flame  and  quietly  bend  to  the  desired 
angle.  In  case  no  wing-top  is  available,  the  tube  may 
be  heated  in  the  same  way  in  an  ordinary  illuminating 
burner.  The  carbon  deposited  on  the  tube  is  readily 
removed,  after  cooling,  by  rubbing  with  filter-paper. 

Drawing  the  Tube. — Heat  as  before  in  wing-top  or  illu- 


4  HOUSEHOLD    CHEMISTRY 

minating  burner;  when  soft,  remove  from  the  flame  and 
quietly  but  steadily  draw  apart.  On  cooling,  the  tube 
may  be  cut  with  a  file  at  any  spot,  and  will  furnish  two 
pointed  tubes.  These  are  used  for  dropping  tubes,  by 
cutting  to  the  desired  length  and  rounding  the  ends  in 
the  flame. 

Closing  the  Tube  and  Blowing  Small  Bulbs. — Select  a 
tube  with  thick  walls,  cut  off  a  piece  about  a  foot  long, 
heat  the  square-cut  end  in  the  upper  part  of  the  ordi- 
nary Bunsen  flame,  revolving  the  tube  continuously  while 
heating;  in  a  short  time  the  tube  will  close.  To  blow  a 
bulb  continue  the  heat  for  a  few  minutes  longer,  then 
remove  and  blow  quietly  but  strongly  into  the  open  end 
of  the  tube,  continue  the  air  pressure  until  the  desired 
diameter  has  been  reached,  but  on  no  account  attempt 
to  make  a  bulb  of  more  than  double  the  diameter  of  the 
original  tube,  as  in  this  case  the  walls  will  be  too  thin. 
If  it  has  been  impossible  to  blow  a  bulb  of  the  desired 
size  in  one  operation,  the  tube  may  be  reheated  and  blown 
again  until  the  desired  diameter  has  been  reached. 

Glass  rod  may  be  cut,  bent  and  rounded  in  manner 
similar  to  tubing. 

CONSTRUCTION  AND  USE  OF  THE  WASH-BOTTLE 

Select  a  clean  eight-ounce  wide-mouthed  bottle,  fit  to 
it  a  rubber  stopper  pierced  with  two  holes.  Now  cut 
two  pieces  of  one-fourth-inch  glass  tubing,  six  and  ten 


CONSTRUCTION    AND    USE    OF    THE    WASH-BOTTLE         5 

inches  long,  heat  the  long  piece  in  the  wing-top  flame 
about  three  inches  from  the  end,  when  soft  remove  from 
the  burner  and  bend  to  an  angle  of  45°.  Heat  and  bend 
the  shorter  piece  in  the  middle  to  an  angle  of  135°,  round 
both  ends  of  each  tube  in  the  flame,  when  cold,  moisten 
one  end  of  the  short  tube  with  saliva  and  push  it  through 
one  hole  of  the  stopper,  proceed  in  the  same  way  with 
the  longer  tube,  but  push  it  nearly  up  to  the  bend,  so 
that  when  the  stopper  is  inserted  in  the  bottle  the  other 
end  will  just  clear  the  bottom.  Cut  a  piece  of  black 
rubber  tubing  two  inches  long,  slip  one  "end  over  the 
longer  tube,  make  a  jet  by  cutting  off  two  inches  of  the 
pointed  end  of  a  dropping  tube,  round  the  rough  end, 
and  when  cool  push  it  into  the  rubber  tube.  The  bottle 
is  complete  and  ready  for  filling  with  cold  water.  By 
blowing  into  the  short  tube,  a  fine  jet  of  water  will  issue 
from  the  nozzle ;  by  tipping  the  bottle  upside  down,  a 
larger  stream  will  issue  from  the  shorter  tube. 

Wash-bottles   for  hot  liquids   are  made  in  the   same 
way,  using  a  thin  glass  flask  instead  of  a  bottle. 


Part  I 


Chapter  I 

FUELS 

Fuels  are  materials  used  for  producing  heat;  they 
must  be  capable  of  uniting  with  oxygen  under  easily 
obtainable  conditions  and  of  evolving  much  heat  energy 
during  the  process  of  combustion.  Occurring  as  gases, 
liquids  and  solids,  carbon  and  its  compounds  largely  fill 
the  required  conditions. 

Classification:  A  logical  arrangement  of  the  fuels 
would  result  as  follows: 


Pure  fuels 


Impure  fuels 


Gases 


Liquids 


Solids 


Solids 


[  Natural 

1 
[  Artificial 

f  Hydrogen 
\  Hydrocarbons 
(Carbon 
monoxide 

(Natural 
Artificial 
(  Natural 

I  Hydrocarbons 
Hydrocarbons 
J  Alcohols 
{  Hydrocarbons 
Anthracite 

I  Artificial 

J  Coke 
*  Charcoal 

Natural 

[  Soft  coal 
j  Peat 

I  Woods 

Coals,  petroleum  and  natural  gas  are  evidently  of  plant 
and  animal  origin,  produced  by  the  natural  method  of 


FUELS  7 

decomposition  similar  to  the  process  of  dry  distillation 
described  on  page  9. 

The  terms  pure  and  impure  are  used  in  a  restricted 
sense,  the  former  signifying  that  the  substance  is  ready 
for  direct  combustion,  while  in  the  latter  case  a  number 
of  complicated  chemical  changes  must  take  place  before 
combustion  is  possible.  This  is  explained  in  detail  in 
the  discussion  of  the  composition  of  wood. 

Historical:  Woods  both  hard  and  soft  and  charcoal 
have  been  used  from  the  earliest  times.  Peat,  a  form  of 
partly  carbonized  turf,  was  the  main  fuel  of  European 
countries  during  the  Middle  Ages  and  is  still  in  use. 
Soft  coal  came  into  use  during  the  I5th  century,  while 
gas  and  hard  coal  were  first  employed  in  the  early  part 
of  the  I9th  century,  and  hydrocarbons  about  the  mid- 
dle of  the  same  epoch.  Alcohol  is  just  coming  into  gen- 
eral use  in  our  own  times. 

Impure  solid  fuels  on  account  of  more  extended  use 
will  be  first  discussed. 

COMPOSITION   OF  WOOD,  PEAT  AND  SOFT  COAL 

Wood,  peat  and  soft  coal  are  such  impure  forms  of 
fuel  and  must  undergo  so  many  and  such  complicated 
chemical  changes  before  they  are  capable  of  yielding 
heat,  that  their  actual  fuel  value  is  frequently  over-esti- 
mated and  rarely  understood  by  the  consumer.  The  fol- 
lowing is  a  brief  and  simple  statement  of  composition 
and  changes  to  be  expected. 


8  HOUSEHOLD    CHEMISTRY 

Wood  contains,  moisture,  (HaO) ;  resin,  (CAH^)  ; 
starch,  gum,  and  cellulose,  «(CSH10O5);  oil,  (CrH/X)  ; 
mineral  matter,  or  ash. 

Considerable  heat  is  required  to  drive  off  the  mois- 
ture and  raise  the  starch,  cellulose,  etc.,  to  such  tempera- 
tures that  they  will  decompose,  yielding  gases  of  a  com- 
bustible nature;  for  example  CO,  CH4,  C2H4,  C2H2,  H, ; 
in  this  decomposition  H2O  is  formed  and  must  be  driven 
off  as  a  gas,  much  heat  is  also  absorbed  by  the  ash  in 
forming  new  chemical  compounds.  In  fact  the  fuel  effi- 
ciency of  wood  depends  entirely  upon  the  relative  vol- 
umes of  combustible  gas  and  charcoa.1  furnished,  and 
as  the  charcoal  or  carbon  is  the  best  solid  fuel,  the  wood 
furnishing  the  largest  proportion  of  carbon  in  this  form 
is  the  best  fuel,  hence  we  find  it  advantageous  to  use 
hardwood.  It  must  be  understood  that  carbon  or  charcoal 
at  a  red  heat  combines  with  a  limited  amount  of  oxygen 
and  forms  a  combustible  gas,  carbon  monoxide,  CO,  a 
fuel  of  the  highest  heating  efficiency. 

Soft  coal,  a  partly  carbonized  plant  product,  produces 
less  water  by  chemical  change  and  yields  the  combustible 
gases  and  carbon  (coke)  in  larger  proportion. 

Hard  coal  is  superior  to  soft,  since  it  is  a  purer  form 
of  carbon  and  yields  very  little  combustible  gas.  It  is 
difficult  to  maintain  the  requisite  temperature  of  decom- 
position during  such  varied  changes,  hence  we  note  the 
dense  smoke  (carbon)  given  off  by  wood  and  soft  coal 


FUELS  9 

fires,  this  may  be  partially  overcome  by  adding  the 
fresh  fuel  in  small  portions,  so  that  the  necessary  high 
temperature  may  not  be  lowered.  An  illustration  of  the 
behavior  of  wood,  peat  and  soft  coal  is  given  in  the 
following  experiments.  The  process  involved  is  known 
as  Dry  or  Destructive  Distillation,  one  of  the  earliest 
methods  of  Organic  Analysis,  still  of  great  commercial 
value. 

Take  a  piece  of  ^-inch  glass  tubing,  about  I  foot  long, 
draw  out  one  end  to  a  fine  jet,  then  heat  the  tube  in  the 
middle  and  bend  at  right  angles  round  the  large  end  in 
the  flame  and  when  cold  insert  it  in  a  perforated  cork. 
Now  place  3  or  4  pieces  of  dry  hardwood  I  inch  long,  % 
inch  square  in  a  6"  X  i"  hard  glass  test-tube,  pushing 
them  down  to  the  end  of  the  tube,  insert  the  cork  and 
clamp  the  tube  and  contents  in  a  slightly  inverted  and 
inclined  position  on  the  ring  stand.  Gently  heat  the  tube 
with  a  broad  flame,  from  the  mouth  upward.  From  time 
to  time  try  the  exit  tube  with  moist  blue  litmus  paper, 
and  then  with  the  flame,  continue  the  heating  until  the 
pieces  of  wood  appear  to  be  completely  charred  and  no 
vapor  is  visible  at  the  exit,  but  avoid  burning  the  cork. 
Before  allowing  the  tube  to  cool,  carefully  remove  the 
cork,  collect  any  liquid  in  the  tube  in  another  test-tube, 
close  the  ignition  tube  with  a  fresh  cork,  and  allow  it 
to  cool.  Observe  the  odor  and  general  character  of  the 
liquid  in  the  test-tube,  add  an  equal  volume  of  water  and 


IO  HOUSEHOLD    CHEMISTRY 

shake  well,  let  the  tube  stand  five  minutes  and  filter 
through  with  wet  paper,  test  the  watery  fluid,  commer- 
cially known  as  pyroligneous  acid,  with  litmus  paper. 
When  the  ignition  tube  is  cold  remove  the  charred  mate- 
rial, carefully  observe  its  character  with  a  magnifying 
glass,  and  make  a  rough  sketch  of  its  structure,  float  a 
small  piece  on  water,  then  boil  it  for  ten  minutes,  ex- 
plain the  result.  Heat  another  piece  in  the  flame,  held  by 
forceps  and  finally  burn  it  to  ash  in  a  porcelain  dish, 
cool  and  add  water,  test  liquid  with  litmus  paper,  then 
with  a  drop  of  dilute  acid,  make  flame  test  on  resulting 
liquid  with  clean  platinum  wire  and  blue  glass.  Make  a 
similar  experiment  with  soft  coal ;  observe  that  the  vapor 
is  first  alkaline  and  finally  acid.  Note  any  difference  in 
the  products  of  distillation  and  ash  of  soft  coal  and  of 
wood.  Another  test  should  be  made  with  hard  coal  for 
comparison.  Arrange  the  results  of  these  experiments 
in  tabular  form  as  follows,  noting  the  comparative  quan- 
tities of  products  evolved. 

Gas  Vapor  Carbon  Ash 

Wood 

Soft  coal 

Hard  coal 

VALUATION  OF  COALS  AND  WOOD  FOR  FUEL 
PURPOSES 

To  determine  the  value  of  coal  or  wood  for  fuel  pur- 


FUELS  II 

poses,  proceed  as  follows:  Take  one  gram  of  pulverized 
coal  or  small  pieces  of  wood  in  a  weighed  crucible,  dry  at 
120°  C.  with  cover  off,  cool  and  weigh,  the  loss  is  water. 
Heat  the  crucible  with  cover  on  in  a  strong  Bunsen  flame 
for  seven  minutes,  cool  and  weigh,  the  loss  is  volatile 
combustible  matter  (tar,  smoke,  etc.)-  Heat  again  with 
cover  off  until  nothing  remains  but  ash.  This  operation 
will  require  some  time;  cool  and  weigh,  the  loss  is  fixed 
carbon  (actual  fuel).  Subtract  the  weight  of  the  crucible, 
the  difference  is  ash. 

Each  student  should  make  a  qualitative  analysis  of  the 
ash  of  wood,  hard  and  soft  coal,  from  specimens  fur- 
nished by  the  instructor,  preparing  the  material  accord- 
ing to  the  following  method. — Extract  about  one  gram 
of  the  weighed  ash  on  a  small  (7  cm.)  filter  several 
times  with  50  cc.  of  boiling  distilled  water;  mark  this 
water  extract  and  reserve  for  test.  Now  extract  the 
residue  with  the  same  amount  of  hot  dilute  HNO3  until 
the  final  residue  is  white  or  nearly  so;  this  is  silica  or 
insoluble  silicate. 

The  aqueous  and  acid  solution  should  be  tested  sepa- 
rately for  the  following  metal  and  acid  ions :  potassium, 
sodium,  calcium,  magnesium,  iron,  sulphates,  carbonates, 
chlorides  and  phosphates,  according  to  the  scheme  given 
on  the  following  pages. 


12  HOUSEHOLD    CHEMISTRY 

SCHEME  FOR  THE  SEPARATION  AND  DETECTION  OP  THE  ANIONS, 

CO3,  PO4,  SO4  AND  Ci,  AND  THE  CATIONS  FE,  CA,  MG, 

NH4,  NA  AND  K. 

The  substance  occurring  in  solid  form.  In  the  case  of  a  liquid 
only  the  acid  need  be  added. 

Treat  a  small  portion  of  the  powder  with  HjOand  enough  HNO3 
to  make  the  solution  acid,  boiling  toward  the  close  of  the  operation, 
only  a  small  residue  should  remain  at  this  point ;  if  otherwise  add 
a  little  more  acid  and  boil  again,  cool  and  filter,  rejecting  any  resi- 
due. The  filtrate  must  be  perfectly  clear  before  proceeding  with 
the  analysis  ;  if  it  is  not,  filter  once  more.  Note  whether  there  is 
any  effervescence  when  the  mixture  of  water  and  acid  is  poured 
upon  the  powder  ;  if  so,  it  indicates  the  presence  of  carbonates, 
COS.  The  gas  evolved  should  be  passed  into  clear  limewater, 
which  will  cloud  if  CO2  is  present. 

The  clear  solution  is  now  divided  into  three  parts  A  =  yz ,  B  =  #, 

c=#. 

Operation  with  solution  A%. 

Add  an  equal  bulk  of  ammonium  chloride  and  then  ammonium 
hydroxide,  NH4OH,  until  distinctly  alkaline,  (odor  of  ammonia  is 
sufficient);  boil  the  mixture.  If  any  precipitate  forms,  filter  the 
mixture  ;  wash  with  one  change  of  water. 

Ppt.  ferric  hydroxide,  a  brown  Filtrate,  clear  and  colorless, 
gelatinous  mass,  dissolve  this  while  still  warm  add  ammonium 
on  a  filter  by  pouring  over  it  a  carbonate,  shake  well,  allow  the 
small  quantity  of  hot  dilute  hy-  ppt.  to  settle  and  cautiously  add 
drochloric  acid ;  collect  the  a  little  more  ammonium  carbon- 
clear  yellow  filtrate  and  add  to  ate,  if  no  further  cloud  occurs, 
it  a  few  drops  of  ammonium  enough  has  been  used ;  now 
thiocyanate ;  a  deep  blood  red  pour  the  mixture  upon  a  filter 
color  indicates  Iron.  and  wash  with  one  charge  of 

water. 


Ppt.  calcium  carbonate,  a 
white  granular  mass,  dissolve 
this  in  the  least  possible  quantity 
of  acetic  acid  on  the  filter.  To 
the  clear  colorless  solution  add 
ammonium  hydroxide  until  al- 
kaline, and  an  equal  bulk  of 
ammonium  oxalate  ;  boil  the 
mixture.  A  white  granular 
ppt.  of  calcium  oxalate  indi- 
cates calcium.  This  should  give 
a  red  flame  on  heated  platinum 
wire. 


Operation  with  B 


Filtrate,  clear  and  colorless. 
Divide  into  two  equal  parts  A 
and  B. 

To  A  add  sodium  phosphate 
and  ammonium  hydroxide  and 
shake  well ;  if  ppt.  does  not 
appear  at  once,  cool  the  mixture. 
A  white  crj'stalline  ppt.  indi- 
cates magnesium.  If  magnesia 
has  been  found  in  A,  pour  B  in- 
to a  clean  porcelain  dish  and 
evaporate  off  the  liquid.  Then 
dry,  heat  until  white  fumes  (am- 
monium salts)  are  no  longer 
evolved.  Cool  and  add  a  small 
amount  of  water,  filter,  reject 
the  residue.  Add  two  drops  of 
hydrochloric  acid  to  the  clear 
filtrate.  Dip  in  it  a  clean  plati- 
num wire  and  test  in  the  flame. 
A  yellow  color  indicates  sodium, 
a  violet  flame  potassium  (both 
to  be  viewed  through  blue 
glass).  Potassium  may  be  pres- 
ent even  though  the  flame  is 
yellow  ;  in  this  case  add  to  the 
filtrate  a  few  drops  of  platinic 
chloride  and  shake  the  mixture. 
A  yellow  crystalline  ppt.  indi- 
cates potassium. 


Make  strongly  alkaline  with  potassium  or  sodium  hydroxide, 
boil  and  hold  a  piece  of  moistened  pink  litmus  paper  in  the  vapor 
arising  from  the  boiling  mass,  being  careful  that  none  of  it  is 


14  HOUSEHOLD    CHEMISTRY 

spattered  on  the  paper.  The  paper  turning  blue  when  moist  and 
back  again  to  pink  when  dry,  indicates  ammonia.  Where  the 
quantity  is  large  the  odor  is  distinctive. 

Operation  with  C  %. 

Divide  into  three  equal  portions. 
Part  I. 

Add  to  this  a  few  drops  of  silver  nitrate ;  a  white  curdy  ppt.  of 
silver    chloride,     soluble    in    ammonium    hydroxide,     indicates 
Chlorides. 
Part  II. 

Add  two  drops  of  hydrochloric  acid  and  a  little  barium  chloride, 
a  white  crystalline  ppt.  of  barium  sulphate  giving  a  green  flame 
on  heated  platinum  wire  indicates  Sulphates. 
Part  III. 

Add  a  few  drops  (not  more  than  10)  to  one  inch  of  ammonium 
molybdate  in  a  6  in.  tube.  Heat  the  mixture  in  boiling  water 
about  two  minutes.  A  yellow  crystalline  ppt.  of  ammonium  phos- 
phomolybdate  indicates  phosphates. 

From  the  results  of  the  above  tests  the  student  is  re- 
quired to  report  any  difference  in  composition  of  the 
ash  and  quantity  of  ingredients. 

The  quantity  of  ash  in  coals  is  always  greater  than  in 
wood,  owing  to  the  presence  of  foreign  mineral  sub- 
stances such  as  silica,  lime  and  sulphide  of  iron  derived 
from  the  earthy  strata  in  which  the  coal  is  deposited. 

Fuel  dust  collecting  in  stove  pipes  and  flues  where 
hard  coal  is  burned,  contains  sulphate  of  ammonia,  when 
cool  this  salt  absorbs  water  and  attacks  iron  rapidly 


FUELS  15 

corroding  the  pipes.  This  fact  explains  the  necessity  of 
cleaning  the  smoke  pipes  of  furnaces  and  stoves  in  the 
spring  of  the  year  when  the  heating  apparatus  is  no 
longer  used. 

Experiment. — Collect  some  of  the  light  gray  dust  from 
a  smoke  pipe,  treat  about  one  gram  with  boiling  water 
on  a  filter,  pouring  the  liquid  through  several  times. 
Reserve  the  residue  and  test  the  liquid  in  the  usual  man- 
ner for  ammonia  and  sulphates. 

Extract  the  residue  still  on  the  filter-paper  with  boil- 
ing dilute  HC1  until  the  residue  is  light  in  color,  this  is 
mainly  silica  from  the  coal  ash,  test  the  acid  filtrate  for 
ferric  iron  and  lime  in  the  usual  manner. 

Liquid  Fuels. — Alcohols,  and  hydrocarbons  in  the  form 
of  gasoline  or  naphtha,  and  kerosene. 

The  hydrocarbon  fuels  are  highly  inflammable  liquids 
distilled  from  coal  or  crude  petroleum  by  a  destructive 
process  known  as  "cracking"  in  which  complicated  hydro- 
carbons break  up  and  yield  simpler  products.  Any  color 
or  objectionable  odor  is  removed  by  treatment  with  oil 
of  vitriol  (Cone.  Commercial  Sulphuric  Acid)  followed 
by  caustic  soda  and  filtration  through  Fuller's  earth. 

Benzine  an  intermediate  product  while  not  used  as  a 
fuel,  serves  as  a  convenient  solvent  for  fats  and  oils, 


l6  HOUSEHOLD    CHEMISTRY 

and  by  many  is  preferred  to  gasoline  for  this  purpose 
on  account  of  greater  security  in  handling. 

At  temperatures  slightly  above  normal  these  hydrocar- 
bons readily  combine  with  oxygen  producing  intense  heat 
and  yielding  water  and  carbon  dioxide  as  products  but 
no  ash,  with  too  small  supply  of  oxygen  the  temperature 
of  combustion  is  much  lowered  and  a  large  part  of  the 
carbon  is  not  consumed  and  escapes  in  a  free  state  pro- 
ducing a  yellow  flame  and  if  in  great  excess  much  black 
smoke.  A  very  familiar  phenomenon  in  kerosene  lamps. 

With  great  excess  of  oxygen,  as  when  the  hot  vapor  of 
these  liquids  is  mixed  with  many  times  its  volume  of  air, 
the  combustion  is  so  rapid  as  to  produce  an  explosion 
(automobile  engine).  When  using  these  products  for 
fuel  purposes  care  must  be  taken  that  these  last  condi- 
tions do  not  exist.  Hence  as  a  measure  of  safety  the 
lamp  or  stove  reservoir  is  kept  well  filled  and  cool.  The 
following  simple  experiment  will  serve  to  impress  these 
important  facts  on  the  student's  mind. 

Pour  not  more  than  one  or  two  drops  of  clean  gasoline 
into  a  clean  dry  wide  mouth  bottle  of  12  to  16  ozs. 
capacity,  stir  the  vapor  for  a  moment  with  a  hot  glass 
or  iron  rod  and  bring  a  lighted  match  over  the  mouth 
of  the  bottle,  a  slight  but  perceptible  explosion  should 
result  with  or  without  blue  flame. 

Pour  a  teaspoonful  of  the  same  liquid  in  a  shallow 
porcelain  dish  or  saucer,  apply  the  lighted  match  and 


FUELS  17 

note  the  yellow  flame,  but  no  explosion.  Quench  by 
covering  with  cloth,  stiff  cardboard  or  any  article  that 
will  exclude  air. 

Gasoline  is  used  quite  largely  in  some  localities  as  a 
source  of  heat,  being  consumed  in  the  so-called  blue 
flame  stove  which  operates  by  heating  the  liquid  to  such 
a  temperature,  air  being  excluded,  that  vapor  forms  rap- 
idly and  under  slight  pressure,  it  is  then  conducted  to 
the  burner  (Bunsen)  mixed  with  the  proper  amount  of 
air  and  burns  with  a  blue  flame. 

These  stoves  and  heaters  are  perfectly  safe  as  long  as 
they  are  kept  clean,  do  not  leak  liquid,  are  kept  well 
filled  and  furnished  with  good  gasoline. 

The  quality  of  gasoline  may  be  determined  by  the  fol- 
lowing tests: 

1.  Observe  the  color,  it  should  be  white  as  water. 

2.  Clearness,  if  cloudy  dirt  or  water  is  present ;  evapo- 
rate a  small  quantity  in  a  clean  porcelain  dish  over  warm 
water    (no  flame)    and  examine  the  residue,  also  filter 
some  through  clean  dry  chamois  skin,  water  and  dirt  will 
remain  on  the  skin.     It  is  a  wise  precaution  for  users  of 
gasoline  for  any  purpose  to  filter  as  above  before  using. 

3.  Test  with  delicate  litmus  paper,  it  should  be  neutral. 

4.  Determine   the   specific   gravity   with   the   Beaume 
hydrometer  for  light  liquids;  it  should  register  68°-?20. 

5.  In  burning  it  should  give  off  no  odor  of  hydrogen 


l8  HOUSEHOLD    CHEMISTRY 

sulphide  or  sulphur  dioxide,  nor  blacken  a  strip  of  lead 
acetate  paper  held  well  above  the  flame. 

Kerosene,  erroneously  called  an  oil,  is  much  more 
extensively  used  and  widely  known;  it  is  probably  the 
cheapest  and  best  liquid  illuminating  agent  of  the  present 
day.  The  ordinary  kerosene  wick  lamp  is  so  well  known 
as  to  need  no  explanation.  Kerosene,  however,  is  used 
in  blue  flame  stoves,  such  as  the  Khotal,  etc.,  and  al- 
though more  troublesome  to  manipulate  is  preferred  by 
most  people  because  the  danger  is  minimized. 

Kerosene  should  successfully  stand  tests  i,  2,  3,  5, 
given  under  gasoline.  The  specific  gravity  should  be  48° 
Beaume.  In  addition,  the  following  known  as  the  Flash 
Test  is  prescribed  by  the  states  of  New  York,  Massa- 
chusetts, etc. 

Flash  Test. — Half  fill  a  200  cc.  beaker  with  kerosene, 
place  over  warm  water,  stir  gently  with  an  accurate 
Fahrenheit  thermometer  and  heat  slowly,  not  more  than 
two  degrees  rise  per  minute,  until  a  small  open  flame 
brought  over  the  mouth  of  the  beaker  causes  a  blue 
flame  and  slight  explosion.  Note  the  temperature,  it  is 
the  flash  point  and  should  not  be  lower  than  100°  Fahr. 

Kerosene  which  will  conform  to  these  tests  is  safe. 

Kerosene  and  gasoline  are  unsaponifiable ;  to  prove  this 
fact  use  kerosene,  heating  a  small  sample  with  one- 
seventh  of  its  volume  of  strong  caustic  soda  solution 


FUELS  19 

(38° -40°  Be)  for  ten  or  fifteen  minutes  over  hot  water 
and  stirring  often,  then  allow  the  mixture  to  cool,  what 
happens,  does  the  product  resemble  soap  in  any  way? 

Kerosene  is  often  called  an  oil,  is  this  statement  cor- 
rect? 

Alcohols. — Of  this  series,  only  methyl  or  wood  alcohol 
and  ethyl  or  grain  alcohol,  are  used  as  fuels.  Lately  a 
mixture  of  the  two  (90  pts.  ethyl,  9  pts.  methyl  -f-  I  pt. 
benzine)  has  come  into  general  use  under  the  name  of 
denatured  alcohol;  it  is  essentially  ethyl  alcohol  and  will 
be  treated  as  such.  Methyl  alcohol,  CH3OH  or  HCH2OH, 
is  produced  commercially  by  the  dry  distillation  of  wood 
and  known  as  pyroligneous  or  wood  spirit;  it  contains 
light  wood  tar,  acetone,  and  acetic  acid  which  should  be 
completely  removed  before  using,  leaving  a  bland  mild 
smelling  liquid  similar  to  ethyl  alcohol  known  as  Co- 
lumbian Spirit.  Much  of  the  ordinary  wood  alcohol  is 
quite  impure.  Tar  and  acetone  are  easily  distinguished 
by  the  color  and  odor,  especially  if  gently  heated;  acid 
is  readily  shown  by  litmus  paper.  The  supposed  poison- 
ous character  of  methyl  alcohol  is  due  entirely  to  im- 
purities. 

As  a  burning  fluid  methyl  alcohol  is  distinctly  inferior 
to  grain  alcohol.  The  following  equation  shows  the  chemi- 
cal change  during  complete  oxidation ;  2CH3OH-}-3O2=: 
4H2O+2CO2. 

By  partial  oxidation,  using  hot  copper  oxide,  methyl 


2O  HOUSEHOLD    CHEMISTRY 

alcohol  is  converted  into  formaldehyde  according  to  the 
following  equation: 

CH3OH+CuO=HCHO+H2O-hCu. 
This  serves  as  a  valuable  test  for  identifying  methyl  al- 
cohol and  may  be  carried  out  in  the  following  manner. 
Heat  a  strip  of  sheet  copper  red-hot  in  the  upper  part  of 
the  Bunsen  flame,  and  immediately  drop  it  into  a  test-tube 
half  full  of  the  alcohol,  wait  until  the  first  violent  efferves- 
cence has  passed  and  then  observe  the  odor  of  the  liquid 
in  the  tube  and  the  bright  appearance  of  the  copper  strip. 

In  order  to  obtain  formaldehyde  in  quantity,  the 
warm  vapor  of  methyl  alcohol  is  passed  over  heated 
copper  oxide  in  a  tube  and  the  product  cooled  with  ice. 

Formaldehyde  will  be  treated  more  in  detail  under 
antiseptics. 

Methyl  alcohol  is  more  volatile  than  ethyl  alcohol,  hence 
the  loss  in  handling  and  while  standing  in  lamps  is  greater. 
By  further  oxidation  methyl  alcohol  yields  formic  acid: 
CH8OH+Oa=HCOaH+HaO. 

Ethyl  or  grain  alcohol :  C2H5OH  or  CH3CH3OH.  Pre- 
pared by  the  fermentation  of  glucose  or  maltose  by  means 
of  yeasts  and  distillation  of  the  product.  It  is  a  color- 
less liquid  with  pleasant  and  characteristic  odor,  usually 
containing  about  95  per  cent,  of  pure  alcohol  and  the 
balance  water  and  small  amounts  of  impurities,  acetic 
acid  and  acetone  more  especially;  these  are  not  particu- 


FUELS  21 

larly  objectionable  if  the  liquid  is  to  be  used  for  generat- 
ing heat  or  general  solvent  purposes,  but  in  many  chemi- 
cal operations  further  purification  is  necessary.  Alcohol 
boils  at  78°-8o°  C. 

When  burned  in  lamps  or  stoves  best  of  the  wickless 
type,  the  following  changes  take  place: 

C2H5OH+3O2=2CO2+3H2O. 

Comparing  this  equation  with  that  of  methyl  alcohol  on 
page  19  it  will  be  seen  that  the  amount  of  CO,  is  doubled, 
hence  it  is  fair  to  assume  that  the  heating  effect  is  great- 
er ;  ethyl  alcohol  is  less  volatile  than  methyl,  therefore  loss 
by  evaporation  during  use  is  less. 

Tests  on  alcohol. 

Determine  the  boiling-point  of  95  per  cent,  alcohol  by 
distilling  100  cc.  in  a  small  flask  fitted  with  a  thermome- 
ter and  condenser.  Determine  the  acidity  of  10  cc.  of  al- 
cohol with  N/io  alkali;  report  percentage  of  acidity  in 
terms  of  acetic  acid. 

Determine  the  specific  gravity  of  alcohol  by  means  of 
the  hydrometer  and  check  the  result  by  the  Westphal 
balance. 

Heat  10  cc.  of  alcohol  with  an  equal  volume  of  strong 
caustic  soda  (20  per  cent.)  for  some  minutes  over  boil- 
ing water,  a  dark  yellow,  or  red  coloration  indicates 
aldehyde. 

To  10  cc.  of  alcohol  add  I  cc.  of  iodine  solution,  heat 


22 


gently  and  add  strong  sodium  carbonate  solution  slowly 
until  the  color  disappears,  notice  the  odor  of  iodoform 
and  when  cold  examine  some  of  the  precipitate  under  the 
microscope;  pale  yellow  hexagonal  plates  appear  on  the 
field. 

Heat  10  cc.  of  alcohol  with  i  cc.  of  K2Cr2O7  solution 
acidified  with  sulphuric  acid,  notice  the  reduction  of  the 
chromium  to  base  and  the  odor  of  aldehyde. 

Dilute  I  cc.  of  neutral  alcohol  to  20  with  ordinary  tap 
water,  add  a  small  quantity  of  vinegar  ferment,  pour  the 
mixture  in  a  small  wide-mouthed  bottle  covering  loosely 
with  cotton,  and  allow  the  whole  to  stand  several  days 
in  a  warm  place,  finally  filter  and  test  for  acetic  acid. 

Pure  alcohol,  free  from  aldehyde  and  acid  for  chemical 
purposes,  can  easily  be  made  from  the  ordinary  95  per 
cent,  variety  or  even  waste  alcohol  by  allowing  it  to  re- 
main for  several  days  in  contact  with  slightly  rancid  tal- 
low or  grease  and  subsequently  filtering,  distilling,  and 
neutralizing  the  product. 

On  account  of  the  high  price,  due  to  the  government 
tax,  ethyl  alcohol  was  formerly  little  used  for  heat  and 
power  purposes,  but  since  the  introduction  of  denatured 
alcohol,  the  cost  has  fallen  to  fifty  cents  per  gallon  and 
the  use  enormously  increased.  At  the  present  price, 
it  is  little  more  expensive  to  use  than  gasoline  and  far 
safer  and  pleasanter  to  handle. 

Gas   consisting  of  hydrogen,    carbon   monoxide,    and 


FUELS  23 

various  hydrocarbons  is  the  ideal  fuel.     There  are  five 
varieties  in  use,  viz. : 

f   Natural  gas 

!    Water  gas 
Gases  proper  1    _     . 

I    Coal  gas 

I  Acetylene 

Naphtha  or  air  gas  J  Cold  air  charged  with  naphtha 

(.      vapor. 

Natural  gas  is  found  in  large  pockets  in  the  earth  in 
many  localities ;  it  is  reached  by  drilling  in  the  same  man- 
ner as  for  oil  or  brine.  Being  under  excessive  pressure 
much  is  lost  before  it  can  be  controlled  and  the  pressure 
reduced  sufficiently  for  household  use.  Consisting  main- 
ly of  hydrogen  and  marsh  gas,  it  has  little  or  no  illumi- 
nating power,  but  is  an  excellent  source  of  heat.  The 
supply  is  gradually  being  exhausted  and  many  wells 
have  ceased  to  yield  any  product.  This  form  of  gas  has 
been  known  from  the  remotest  antiquity,  many  old  shrines 
being  supplied  through  crevices  in  the  earth,  probably 
the  Temple  of  Diana  at  Ephesus  had  a  natural  gas  well. 

Fredonia,  New  York,  was  lighted  with  natural  gas 
as  early  as  1825,  the  supply  being  accidently  discovered 
when  boring  for  salt. 

Water  or  Fuel  Gas. — By  passing  steam  at  high  pressure 
over  white  hot  carbon  Tessie  du  Motay  produced  a  mix- 
ture of  hydrogen  and  carbon  monoxide,  known  as  water 


24  HOUSEHOLD    CHEMISTRY 

gas.     The  equations  for  the  chemical  change  are  as  fol- 
lows: 
4H20+Ca=4Ha+2C02. 


In  order  to  give  the  mixture  illuminating  quality  it  was 
passed  over  gasoline  vapor  and  subsequently  through  a 
hot  retort  to  prevent  condensation  on  cooling;  the  re- 
sulting gas  was  purified  in  the  same  manner  as  coal  gas 
and  yielded  a  product  of  similar  composition  containing 
hydrogen  carbon  monoxide,  marsh  gas,  ethylene  and 
acetylene,  but  in  somewhat  different  proportions  and 
since  it  contains  more  carbon  monoxide  it  is  generally 
regarded  as  a  better  fuel. 

Coal  Gas.  —  From  soft  or  bituminous  coals,  as  gas  can 
be  produced  by  dry  distillation,  see  experiment  on  page 
9.  This  was  the  first  method  used  for  making  gas,  and 
dates  back  to  early  days  of  the  iQth  century.  On  ac- 
count of  the  many  and  valuable  by-products  produced, 
viz.,  ammonia,  coal  tar,  carbolic  acid,  napthalene,  cy- 
anides, etc.,  it  will  probably  be  used  for  many  years  to 
come. 

The  process  consists  in  heating  the  coal  in  large  clay 
retorts,  drawing  off  and  cooling  the  gas  in  order  to  con- 
dense tar,  washing  to  remove  ammonia,  tar,  etc.,  remov- 
ing sulphur  with  lime  or  iron  oxide,  storing  and  deliver- 
ing the  gas  under  slight  pressure.  Essentially  the  same 
process  of  purification  is  used  with  water  gas. 


FUELS  25 

Acetylene  gas,  C2H2,  made  by  the  action  of  water  on 
calcium  carbide  as  follows: 

CaC2+2H2O=C2H24-Ca(OH)2. 

Calcium  carbide  is  prepared  by  heating  a  mixture  of 
lime  and  charcoal  in  the  electric  furnace. 

Either  the  water  is  sprayed  on  the  carbide,  or  finely 
pulverized  carbide  is  sprinkled  in  water. 

Acetylene  is  only  used  in  places  where  ordinary  gas 
cannot  be  obtained,  and  is  generally  used  at  once.  It  may, 
however,  be  stored  in  an  ingenious  manner;  strong  cop- 
per cylinders  are  partly  filled  with  acetone,  and  acetylene 
pumped  in  until  a  certain  pressure  is  obtained.  By  at- 
taching one  of  these  tanks  to  a  lamp,  a  strong  light  may 
be  maintained  for  many  hours.  The  rationale  of  the 
process  is  that  acetone  dissolves  acetylene  under  pressure 
and  slowly  gives  it  up  when  the  tension  is  released. 

Naphtha  Gas. — Many  isolated  country  houses  depend 
for  heat  and  light  on  this  mixture.  Outside  of  the  build- 
ing and  underground,  is  placed  an  iron  tank  for  holding 
the  hydrocarbon,  pipes  lead  to  and  from  the  house.  In  the 
house  cellar  is  placed  a  large  revolving  drum  driven  by 
weights,  for  forcing  air  through  the  gasoline  and  driving 
back  to  the  house  the  vapor  laden  air.  The  process  is 
satisfactory  on  a  small  scale  but  rather  expensive,  de- 
pending wholly  on  the  price  of  the  hydrocarbon. 


26  HOUSEHOLD    CHEMISTRY 

COMPOSITION 

The  constituents  of  illuminating  gas  are  conveniently 
classified  as  follows: 

Impurities  or  diluents  —  oxygen,  carbon  dioxide,  nitro- 
gen. 

Illuminants  —  ethylene,   acetylene. 

Gas  proper  —  hydrogen,  marsh  gas  or  methane,  car- 
bon monoxide. 

The  method  of  procedure  in  the  analysis  is  to  dissolve 
out  or  absorb  carbon  dioxide,  illuminants,  oxygen  and 
carbon  monoxide  in  the  order  named,  using  the  following 
reagents:  caustic  potash  20  per  cent.,  bromine,  alkaline 
pyrogallol,  and  cuprous  chloride.  The  insoluble  residue 
consisting  of  hydrogen,  marsh  gas  and  nitrogen,  is  mixed 
with  oxygen  and  exploded  by  the  electric  spark,  which 
produces  carbon  dioxide,  water  and  nitrogen.  The  fol- 
lowing equations  express  the  chemical  change: 


CH4+202r=C02-f2H20. 

The  volume  of  residual  gas  is  carefully  measured  and 
subtracted  from  the  volume  before  explosion,  leaving  the 
contraction,  due  to  H2O  and  designated  as  C  in  the  fol- 
lowing- formula.  Finally  the  CO2  formed  is  absorbed 
by  KOH,  as  before,  and  the  loss  in  volume  noted;  this 
known  as  D  in  the  formula  is  equal  in  volume  to  the 
original  CH4. 


FUELS  27 

The  volume  of  hydrogen  is  now  calculated  from  these 
data,  according  to  the  formula 


3 

Nitrogen  is  the  difference  between  100  and  the  sum  of 
the  other  constituents  ;  it  should  approximate  four  times 
the  oxygen  found. 

The  value  of  gas  is  expressed  as  candle-power,  a 
standard  sperm  candle  burning  two  grains  per  minute 
being  the  unit;  hence  a  25-candle-power  gas  would  give 
as  much  light  as  25  of  the  candles  burning  simultane- 
ously. 

The  standard  illuminating  burner  consumes  five  cubic 
feet  per  hour  under  a  pressure  of  one  and  a  half  inches 
of  water,  this  is  used  as  a  unit  in  all  gas  calculations. 

Two  styles  of  meters  are  used  —  the  wet  and  the  dry; 
in  the  former  the  gas  passes  through  a  revolving  drum 
partially  submerged  in  water.  The  revolutions  are  regis- 
tered on  dials  by  appropriate  clockwork.  Since  this 
form  of  meter  is  liable  to  freeze  and  must  always  contain 
water,  some  of  which  is  lost  by  evaporation,  it  has  been 
largely  superseded  by  the  dry  meter  which  contains  two 
bellows  alternately  full  and  empty.  A  clockwork  de- 
vice, similar  to  that  used  in  the  wet  meter,  keeps  record 
on  appropriate  dials.  Gas  meters  are  subject  to  public 
test  and  are  allowed  an  error  of  two  per  cent,  either  fast 
or  slow. 
3 


28  HOUSEHOLD    CHEMISTRY 

Hydrogen  sulphide  is  the  only  impurity  in  gas  of  any 
importance ;  by  its  combustion  sulphur  dioxide  and  water 
are  produced,  finally  resulting  in  sulphurous  acid,  which 
readily  attacks  fabrics  and  metals  and  bleaches  many 
colors.  Any  hydrogen  sulphide  escaping  combustion 
blackens  lead  acetate  paper  held  far  enough  above  the 
flame  to  be  uninfluenced  by  the  heat. 

Analyses  of  gas  are  given  below : 

Water  gas  Coal 

Per  cent.  gas 

Carbon  dioxide o.o  o.o 

Illuminants 12.6  6.5 

Oxygen 0.9  0.9 

Carbon  monoxide 27.3  6.8 

Hydrogen 27.7  41.1 

Marsh  gas 27.7  41.6 

Nitrogen 3.8  3.7 

100. o  100.0 

Candle-power  25.04  21.32 

In  a  water  gas,  the  candle-power  is  usually  double  the 
illuminants. 

Chemical  Changes  During  Combustion. — The  common 
burner  can  only  use  gas  of  the  following  composition : 
methane,  CH4,  ethylene,  QjH^,  acetylene,  C2H2,  hydro- 
gen, H2,  and  carbon  monoxide,  CO.  Combustion  pro- 
ceeds according  to  the  following  equations: 

CH4+2O2=CO2-f-2H2O— heat,  no  light. 

2H2+O2=r2H26— heat,  no  light. 

2CO+O2=2CO2— heat,  no  light. 


29 

C2H4=O2— 2H2O+C2— less   heat,   some   light. 

2C2H2+O2=2H2O+2C2— less  heat,  more  light. 

The  Bunsen  burner  mixes  the  gas  with  O2  before 
combustion;  this  affects  only  the  ethylene  and  acetylene 
as  follows : 

C2H4+3O2=2H2O-f  2CO2— heat,  no  light. 

2C2H2-f-5O2— 2H2O+4CO2— heat,  no  light. 

The  following  simple  but  important  experiments  should 
be  performed  by  each  student. 

Conditions  of  Combustion. — Fill  a  250  cc.  wide-mouth- 
ed bottle  with  four-fifths  air  and  one-fifth  gas,  collecting 
it  over  water,  cover  with  a  glass  plate  and  shake  thor- 
oughly. Quickly  replace  the  glass  plate  with  wet  filter- 
paper,  pierce  with  a  pencil  point,  apply  the  flame  and  note 
the  result.  Try  the  same  experiment  using  gas  alone. 
Write  equations  explaining  the  results  of  these  experi- 
ments. 

Products  of  Combustion. — Hold  a  clean  dry  bottle  for 
a  few  moments  over  a  low  Bunsen  flame  and  note  the 
result.  What  compound  is  formed?  Explain  and  write 
equation. 

Substitute  a  pointed  glass  tube  for  the  Bunsen  burner, 
turn  the  gas  low  and  light  at  the  point,  introduce  the 
flame  into  a  clean  dry  bottle  and  hold  it  there  for  a  few 
moments,  note  the  result  and  remove  the  tube.  Again 
introduce  it  under  the  same  conditions  and  note  the 


30  HOUSEHOLD    CHEMISTRY 

result.  Remove  the  tube,  cover  the  bottle  with  a  glass 
plate  and  turn  off  the  gas.  Pour  about  10  cc.  of  lime 
water,  Ca(OH)2,  into  the  bottle,  shake  well,  note  the  re- 
sult, explain,  and  write  the  equation. 

Reading  the  Meter  and  Testing  Burners  and  Stoves. — 
Study  the  dials  and  figure  out  how  they  are  read.  Con- 
nect meter  with  gas  tap  and  lead  rubber  tube  to  burner, 
be  sure  the  meter  is  running  in  the  right  direction.  Light 
the  burner  and  after  an  interval  of  a  few  minutes  note 
the  time  and  meter  record,  exactly  six  minutes  after- 
wards again  read  the  meter,  subtract  the  original  reading 
and  multiply  by  ten,  the  result  will  be  the  number  of 
feet  per  hour  consumed. 

Heat  Consumed  in  Boiling  Water  Under  Varying  Con- 
ditions.— Start  the  burner  as  in  the  first  experiment  and 
note  the  time  and  consumption  of  gas  necessary  to  boil 
one  quart  of  water  in  open  and  closed  vessels  made  of 
sheet  tin,  cast  iron,  aluminium  and  copper.  Does  the 
shape  of  the  vessel  affect  the  result? 

All  of  the  above  experiments  should  be  made  in  a 
quiet  room  free  from  drafts  caused  by  open  doors  and 
windows.  If  stoves  are  being  used  they  should  stand 
on  heavy  sheet  asbestos  in  order  to  avoid  loss  of  heat  due 
to  radiation. 


Chapter  II 


CAKBON  DIOXIDE 

Carbon  dioxide,  CO,,  erroneously  known  as  carbonic 
acid,  is  the  chief  product  of  the  combustion  of  carbon 
and  its  compounds.  It  is  one  of  the  heaviest  of  the 
gases,  density  22,  or  about  one  and  a  half  times  as 
heavy  as  air.  Under  a  pressure  of  59  atmospheres  it 
liquefies  at  20°  C.,  its  critical  temperature  is  31.1°  C.,  sp. 
gr.  of  the  liquid  at  o°  C.  is  0.95.  CO2  dissolves  in  its 
own  volume  of  water  under  N.  T.  P.  conditions.  Under 
a  pressure  of  7  or  8  atmospheres,  a  solution  is  ob- 
tained familiarly  known  as  soda  water.  Carbon  diox- 
ide is  a  very  stable  compound  and  shows  a  tendency  to 
dissociate  only  at  very  high  temperatures :  2CO2— 2CO-f- 
O2 ;  in  the  presence  of  hot  carbon  this  change  takes  place 
at  lower  temperatures  (see  water  gas).  Carbon  dioxide 
attacks  all  metallic  oxides  in  the  presence  of  moisture 
producing  carbonates,  particularly  the  oxides  of  the  al- 
kalies and  alkaline  earths,  viz. :  lime,  CaO,  potash,  K2O, 
and  soda,  Na2O,  which  are  very  unstable  for  this  reason. 

Carbon  dioxide  is  most  easily  prepared  by  attacking 
marble,  CaCO3,  with  dilute  nitric  acid,  HNO3,  which 
forms  a  soluble  by-product  Ca(NO3)2  and  oxidizes  the 
small  amounts  of  organic  matter  present: 

CaCO3+2HNO3=CO2+H2O+Ca(NO3)2. 


32  HOUSEHOLD    CHEMISTRY 

Carbon  dioxide  is  also  evolved  during  the  growth  and 
development  of  bacteria,  notably  the  yeasts  acting  upon 
soluble  carbohydrates,  glucoses,  maltose,  etc. 

C6H12O6=2CO2+2C2H5OH  and  utilized  in  the  leaven- 
ing of  doughs  and  the  preparation  of  effervescing  drinks. 
A  mixture  of  bicarbonate  of  soda  and  acid  potassium 
tartrate,  under  the  name  of  baking  powder,  when  moist- 
ened evolves  CO2  according  to  the  following  equation: 

NaHC03  -f  KHC4H4O6  =  CO2  +H2O+KNaC4H4Oa. 

Liquid  carbon  dioxide  when  released  from  pressure  ab- 
sorbs much  heat  in  passing  into  the  gaseous  state,  this 
fact  is  utilized  in  cold  storage  operations,  the  gas  is  col- 
lected and  recompressed. 

The  water  solution  of  carbon  dioxide  is  feebly  acid 
due  to  the  formation  of  carbonic  acid,  H2CO3,  as  follows : 

H20+C02=H2C03. 

Carbonic  acid  acts  on  all  carbonates,  forming  bicar- 
bonates  in  most  cases  more  soluble  in  water  than  the 
corresponding  carbonates;  familiar  examples  are  the 
bicarbonates  of  lime  and  magnesia,  causing  the  hardness 
in  water  CaCO34-H2CO3=Ca(HCO3)a,  and  baking  soda 
Na2CO3+H2CO3=2NaHCO3. 

At  or  near  the  boiling-point  of  water,  carbonic  acid 
breaks  up  into  CO2-f  H2O,  likewise  the  bicarbonates 
decompose  into  carbonates,  water  and  carbon  dioxide; 


CARBON    DIOXIDE  33 

hence   all   soluble  bicarbonates   should   be   dissolved   in 
cool  water. 

Preparation  of  Bicarbonate  of  Lime. — Dilute  50  cc.  of 
clear  fresh  limewater,  Ca(OH),,,  with  an  equal  volume 
of  water  and  pass  a  rapid  current  of  CO2  through  the 
mixture.  What  is  the  white  precipitate?  Write  the 
equation.  Why  does  the  white  solid  disappear  after  the 
gas  has  been  passing  for  some  time?  Write  the  equa- 
tion. When  the  liquid  is  perfectly  clear,  test  with  lit- 
mus paper,  and  then  boil  one-half  of  it.  Explain  the 
result  by  means  of  an  equation. 

This  experiment  has  a  special  bearing  on  the  soften- 
ing of  water. 

Preparation  of  Sodium  Bicarbonate. — Dilute  25  cc.  of 
strong  ammonia  with  an  equal  bulk  of  water,  cool  and 
saturate  the  liquid  with  salt.  NaCl,  then  pass  a  rapid 
and  continuous  current  of  carbon  dioxide  through  the. 
solution  and  keep  up  the  action  until  no  more  precipi- 
tate forms,  filter  and  wash  with  a  saturated  solution? 
of  sodium  bicarbonate,  dry  and  weigh  the  resulting- 
NaHCO3.  Complete  the  equation: 
NaCl+NH3+H2O+CO2=NaHCO3+.  "r*H1 

The  special  functions  of  carbon  dioxide  to  plant  and 
animal  life  will  be  discussed  in  the  next  chapter. 


Chapter  III 

THE  ATMOSPHERE 

Composition. — Pure  air  is  a  mixture  of  four  parts  of 
nitrogen  and  one  part  of  oxygen.  Other  constituents 
occur  in  small  quantities,  chiefly  water  and  carbon 
dioxide.  The  density  of  the  air  is  approximately 
14.5  in  the  dry  state  and  it  will  support  30  inches  or 
760  mm.  of  mercury  at  the  sea  level.  By  admixture 
with  water  vapor  density  9,  its  weight  and  supporting 
power  decline,  hence  the  barometer  does  not  stand  as 
high  during  the  period  just  preceding  a  storm.  Evident- 
ly the  expression  heavy  is  misplaced  in  this  case.  The 
pressure  of  the  atmosphere  on  each  square  inch  of  sur- 
face is  fifteen  pounds,  but  is  rarely  appreciated,  since  it 
is  exerted  in  all  directions.  The  following  simple  ex- 
periment graphically  demonstrates  this  pressure:  Pour 
two  inches  of  water  into  a  clean  ordinary  half  gallon 
can,  boil  vigorously  and  close  the  opening  with  a  close 
fitting  cork.  Remove  the  burner  and  when  cool  the  can 
will  collapse.  The  can  should  have  a  small  opening  and 
preferably  be  rectangular  in  shape. 

Air  is  slightly  soluble  in  water,  but  its  composition  is 
markedly  different  from  the  atmosphere,  containing  more 
CO2  and  having  its  oxygen  and  nitrogen  in  the  propor- 
tion of  1-3.  Its  exhilarating  effect  in  water  is  well 
known.  Air  is  liquefied  at  a  temperature  of  — 190°  C. 


THE  ATMOSPHERE  35 

Carbon  dioxide  occurs  in  air  to  the  extent  of  0.03  per 
cent.  A  portion  of  this  is  washed  out  by  the  rain  and  com- 
bines with  lime  forming  the  shells  of  molluscs ;  the  larger 
part,  however,  is  utilized  by  the  plant  organism  in  the 
formation  of  starch  and  storing  of  the  sun's  energy. 
This  subject  will  be  discussed  more  in  detail  under  car- 
bohydrates. The  dust  of  air  is  very  variable  in  compo- 
sition and  quantity  but  may  be  classified  as 

Mineral — particles  of  soil,  iron,  glass,  carbon,  etc. 
Organic — Dead — fragments  of  plants,  hairs,  etc. 
Living — pollen,   spores,   and  bacteria. 

The  dust  in  air,  irrespective  of  quality,  curiously  in- 
fluences the  deposition  of  excess  moisture,  causing  it  to 
condense  in  visible  particles;  hence  we  have  fog,  more 
prevalent  the  greater  the  amount  of  dust  in  the  locality, 
as  in  large  manufacturing  cities. 

Dustless  air  can  be  prepared  by  sucking  air  into  a  flask 
through  a  tube  12-15  inches  long  filled  with  cotton. 

Examine  the  dust  sweepings  from  a  window  sill,  look 
for  iron  with  a  magnet,  burn  off  the  organic  matter  and 
note  the  mineral  residue,  extract  some  of  this  with  boil- 
ing dilute  HC1,  note  the  white  residue  of  silica  and  test 
the  solution  for  iron  and  lime. 

A  little  of  the  original  dust  sprinkled  into  milk  will 
cause  it  to  decompose  quickly.  It  will  ferment  weak 
sugar  solution  and  cause  stronger  ones  to  mould.  Try 
these  experiments. 


36  HOUSEHOLD    CHEMISTRY 

Do  not  fail  to  carefully  examine  a  minute  portion  of 
moistened  dust  under  the  microscope  with  low  power. 

Each  student  should  make  the  following  tests : 

1.  Pour  an   inch  of  alkaline  pyrogallol  into  a  short 
broad  test-tube,  close  with  a  rubber  stopper,  invert  and 
mark  the  position  of  the  stopper  and  liquid  on  a  gum 
label  pasted  on  the  outside  of  the  tube,  shake  the  tube 
well,  invert  and  open  under  water,  mark  the  level  of  the 
water  in  the  tube  when  open,  and  explain  the  phenomenon. 

2.  Fasten  one  inch  of  Christmas  candle  to  a  flat  cork, 
float  on  a  shallow  dish  of  limewater,  light  the  candle  and 
invert  a  clean  dry  beaker  over  it,  add  more  limewater 
if  necessary.  Describe  and  explain  the  result.  Try  a  light- 
ed candle  in  the  residual  air,  what  is  the  result  ?  Explain. 

3.  Carbon  Dioxid,  C02. — Expose  a  few  drops  of  lime- 
water  on  a  slide  to  the  air  and  notice  that,  by  the  end 
of  the  lesson,  it  is  cloudy.     Examine  under  the  micro- 
scope the  rhombohedral  crystals  of  calcium  carbonate, 
CaCO3,  and  draw  a  diagram  of  them. 

4.  Hydrogen   Sulphide,   H,S. — Moisten  a   filter-paper 
with  a  solution  of  acetate  of  lead  and  expose  to  the  air 
until  the  end  of  the  lesson.     Notice  the  black  coloration 
due  to  the  formation  of  lead  sulphide.     This  test  works 
very  well  in  gas-lit  rooms. 


THE   ATMOSPHERE  37 

5.  Expose  strips  of  paper,  saturated  with  cobalt  chlo- 
ride or  iodide  and  then  thoroughly  dried,  to  the  air  out 
and  in  doors;  under  moist  conditions,  it  turn  pink. 

Weigh  out  a  small  watch-glass  containing  about  one 
gram  of  fused  calcium  chloride,  wait  about  two  hours 
and  weigh  again.  Note  the  increase  in  weight  largely 
due  to  water. 

Special  functions  of  the  air  constituents  with  regard  to 
plant  and  animal  organisms.  Oxygen  of  the  air  inhaled 
by  the  warm  blooded  animals  combines  with  the  haemo- 
globin in  the  lungs  is  carried  to  the  tissues  where  oxida- 
tion takes  place  and  the  resulting  carbon  dioxide  brought 
back  to  lungs  and  released.  Not  all  of  the  oxygen  in- 
haled is  absorbed  as  the  exhaled  breath  of  human  beings 
contains  in  100  cc.  15.9  cc.  of  oxygen  and  3.7  cc.  of 
carbon  dioxide.  The  carbon  of  the  carbon  dioxide  is 
converted  by  the  plant  into  carbohydrate  which  it  retains 
and  the  free  oxygen  restored  to  the  air. 

Water  serves  as  a  circulating  medium  and  solvent  for 
both  plants  and  animals,  the  former  specially  need  it  for 
complicated  changes,  explained  later  under  hvHrolysis. 

Water  on  account  of  high  heat  capacity  ads  as  a  tem- 
perature regulator,  the  bodily  temperature  being  con- 
trolled by  evaporation  from  the  skin.  3 lost  of  the  bac- 
teria are  harmless  and  useful — such  as  yeasts,  lactic  and 
acetic  acid,  etc. 


Chapter  IV 

WATER 

Physical  Properties. — Water,  hydrogen  monoxide,  H2O, 
the  universal  solvent,  exists  in  three  states  without  change 
of  composition;  as  a  gas,  (steam)  at  100°  C.,  as  a  liquid 
(water)  between  o°  and  100°  C.,  maximum  density,  4°  C.. 
and  as  a  solid  (ice)  below  o°  C.  In  passing  into  the  gas 
state,  the  water  absorbs  537  calories  (  a  calorie  is  the 
amount  of  heat  necessary  to  rai^e  the  temperature  of 
water  one  degree  centigrade),  and  expands  from  I  to 
1728  volumes,  hence  the  expression  a  cubic  inch  of  water 
will  make  a  cubic  foot  of  steam. 

In  the  liquid  state,  water  is  practically  incompressible, 
but  passing  into  the  solid  state,  it  expands  10  per  cent, 
yielding  up  79  calories. 

At  all  temperatures,  water  passes  into  the  vapor  state 
depending  upon  the  condition  of  the  surrounding  atmos- 
phere, whether  saturated  or  not. 

Water  is  used  as  a  standard  of  weight,  one  cubic  cen- 
timeter, at  4°  C.  being  called  one  gram.  In  the  common 
system,  one  pint  of  water  weighs  approximately  one 
pound,  and  one  U.  S.  gallon,  231  cubic  inches,  containing 
eight  pints.  The  weight  of  one  gallon  is  about  8.3  Ibs. 
About  7.5  gallons  make  a  cubic  foot. 

The  boiling-  and  freezing-points  of  water  are  used  as 


WATER  39 

convenient  points  for  standardizing  thermometer  scales; 
in  the  centigrade  system  o°-ioo°,  in  the  Fahrenheit 
32°-2i2°,  in  the  Reaumur  o°-8o°,  all  under  ordinary 
atmospheric  pressure.  'As  a  standard  unit  for  specific 
gravity  measurements,  water  serves  for  liquids  and  solids. 
The  well  known  hydrometer,  an  instrument  for  determin- 
ing the  sp.  gr.  of  liquids,  floats  at  mark  i  in  distilled 
water  of  15.5°  C.  or  60°  Fahr.  On  the  Beaume  scale 
water  is  marked  as  zero. 

Pure  water  is  a  poor  conductor  of  electricity  and  heat, 
but  dissolved  matter  increases  its  conductive  capacity. 

Chemical  Properties. — As  a  chemical  agent,  water  is 
extremely  potent,  acting  usually  as  a  solvent,  but  in 
many  cases  producing  profound  chemical  changes.  Briefly 
the  action  of  water  may  be  classed  as  follows: 

Water  of  solution,  water  of  hydration,  water  of  hy- 
drolysis. 

Water  of  Solution. — When  any  solid,  salt,  niter,  etc., 
dissolves  in  water,  loss  or  gain  of  heat  is  apparent,  but 
on  evaporating  the  liquid,  the  solid  reappears  in  the 
original  form. 

Water  of  Hydration. — The  soluble  substance  eventually 
reappears  on  partial  evaporation  of  the  liquid  in  changed 
form  containing  some  of  the  water  in  the  solid  state 
and  known  as  water  of  crystallization.  Familiar  ex- 
amples are  washing  soda,  alum,  Glauber's  salt,  etc. 


HOUSEHOLD    CHEMISTRY 


Water  of  Hydrolysis.  —  By  double  decomposition,  the 
water  molecule  appears  as  OH,  hydroxyl,  as  in  solutions 
of  caustic  alkalies  and  slaking  lime: 

Na2O+H2O=2NaOH. 
CaO+H2O=Ca(OH)2. 

Or  the  solution  of  non-metallic  oxides, 

S03,  N205,  P205: 
SO3+H2O=SO2(HO)2  or  HaSO4. 
N2O5+H2O=2NOl2HO  or  2HNO3. 
P205+3H20=2PO(HO)3  or  2H3PO4. 

and  the  change  of  starch,  sugar,  etc.  : 
C6H10O3-(-H2O=:C6H12O6. 


Natural  Waters,  Classification.  —  Natural  waters  are 
never  pure,  dissolving  or  holding  in  suspension  gases, 
liquids  and  solids  with  which  they  come  in  contact.  The 
following  is  a  convenient  classification  : 


Natural 
Waters 


Atmospheric 


Terrestrial 


Rain— contain  very  little  dissolved  solids 

Snow 

Fog— but  dust  and  gases  of  the  atmosphere. 

f    Surface — cloudy,  usually  a  large 
amount  of   suspended    matter, 
o        .1        minimum  of  dissolved. 

'  Underground — clear,  minimum  of 
suspended  matter  maximum  of 
dissolved. 


Salt 


f    Brines— over  5  $  soluble  salts. 
\    Sea  Water — 3.6  ;•  solids. 


Mineral— excess    of,    or    unusual     mineral 
matter  and  gases. 


WATER  41 

Potable  or  drinking  water  should  be  clear,  free  from 
odor  and  color,  and  should  contain  not  more  than  twenty 
grains  of  solids  per  U.  S.  gallon,  of  which  not  more 
than  one-half  is  organic  matter. 

The  soluble  mineral  matter  in  water  consists  of  a  mix- 
ture of  the  following  salts: 

Carbonates  ~|  f     Sodium 

Bicarbonates  Potassium 

Sulphates  Calcium 

Chlorides  Magnesium 

together  with  oxide  of  iron  and  silica  in  minute  amounts. 
An  excess  of  chlorides  may  be  due  to  sewage  or  animal 
contamination,  excess  of  lime  causes  hardness,  and  ex- 
cess of  iron  usually  is  apparent  from  the  color  and  is 
probably  due  to  the  solvent  effect  of  organic  matter  in 
the  water. 

On  boiling,  water  loses  its  dissolved  gases,  hence  dis- 
tilled or  sterilized  water  is  flat  or  stale. 

EXPERIMENTS  ON  WATER 

i.  Heat  Conductivity. — Fill  an  eight-inch  test-tube 
two-thirds  full  of  water,  grasp  the  lower  end  of  the  tube 
with  the  fingers  and  hold  in  the  flame  at  a  slight  inclina- 
tion from  the  perpendicular.  Note  that  the  upper  part 
will  boil  before  the  lower  becomes  uncomfortably  hot  to 
hold.  Reverse  the  order  of  heating  and  note  the  same 
result.  Explain. 


42  HOUSEHOLD    CHEMISTRY 

2.  Boiling-Point   Tinder   Atmospheric   Pressure. — Pour 
about  250  cc.  of  distilled  water  into  a  half  liter  round 
bottom  flask  supported  on  a  ring  stand.     Introduce  a 
thermometer  so  that  the  bulb  only  is  immersed  in  the 
liquid  and  apply  heat.     Note  the  point  to  which  the  mer- 
cury rises  when  the  liquid  is  quietly  boiling,  raise  the 
thermometer  bulb  just  out  of  the  liquid  and  boil  again. 
Is  there  any  difference?     Does  the  thermometer  indi- 
cate any  higher  degree  of  heat  when  the  liquid  boils 
violently  ? 

3.  Boiling-Point    Under    Reduced    Pressure. — Select 
a    cork    which    fits    the    flask    tightly,   pierce   a   hole 
through  it  and  insert  a  thermometer.     Now  half  fill  the 
flask  with  water  and  boil  the  liquid.       When  in  active 
ebullition,  close  the  flask  with  the  cork  and  thermometer 
and  withdraw  the  heat.     In  a  few  minutes  the  liquid 
will  cease  to  boil,  then  read  the  thermometer  and  grasp- 
ing the  neck  of  the  flask  with  several  folds  of  a  towel 
hold  it  under  the  cold  water  tap,  what  happens?    Read 
the  thermometer  and  explain. 

4.  Freezing-Point. — Place    a   six-inch    funnel   in  the 
ring  stand  with  drip  cup  beneath,  suspend  a  thermometer 
on  the  same  stand  so  that  the  bulb  is  half  way  down  the 
funnel.     Fill  the  funnel  with  finely  cracked  ice  and  note 
the  lowest  temperature  reached  by  the  thermometer.  Re- 
peat the  experiment,  using  fine  salt  with  the  ice.     Why 
does  the  mercury  go  lower? 


WATER  43 

The   foregoing  experiments  2,  3  and  4  serve  as  ex- 
cellent methods  of  testing  the  accuracy  of  thermometers. 

5.  Influence  of  Soluble  Matter. — Repeat  experiment  2, 
after  dissolving  two  tablespoon fuls  of  salt  in  the  water. 
Note  the  temperature  at  which  the  liquid  now  boils,  cool 
and  take  its  sp.  gr.  and  reserve  for  use  in  experiments 
6  and  14. 

6.  Take  the  larger  part  of  the  liquid  prepared  in  the 
previous  experiment  and  boil  it  down  in  a  small  beaker 
to  one-half  of  its  bulk,  how  does  the  thermometer  stand 
now,  remove  it  and  allow  the  liquid  to  cool  thoroughly. 
Examine  the  crystalline  deposit  with  a  lens,  draw  a  dia- 
gram of  what  you  observe.     Taste  the  residue.     Does 
it  suggest  the  original  salt? 

7.  Make  a  strong  solution  of  sugar  in  water,  take  the 
sp.  gr.  of  the  cold  liquid  and  treat  it  in  the  same  way 
as  the  salt  solution  in  experiment  6. 

8.  Note  the  boiling-point  of  a  mixture  of  equal  vol- 
umes of  water  and  strong  alcohol.     Preserve  the  liquid 
and  return  it  to  the  instructor. 

9.  Water  as  Solvent. — Determine  the  weight  of  salt 
necessary  to  make  a  saturated  solution  (pickle)  at  ordi- 
nary  temperatures.     Use    cold    water   and   shake   well. 
Take  the  sp.  gr.  of  the  liquid  with  a  Beaume  hydrom- 
eter and  record  the  result.     Will  a   fresh  egg  sink  or 
float  in  this  liquid?     Try  it. 

4 


44  HOUSEHOLD    CHEMISTRY 

10.  Hydration  and  Hydrolysis. — Take  half  a  table- 
spoonful  of  dry  pulverized  lime,  (CaO),  add  to  it  an 
equal  volume  of  cold  water,  stir  the  mixture  in 
a  small  porcelain  dish  with  a  thermometer,  adding 
more  water  if  necessary,  record  the  thermometer  rea'd- 
ings  carefully.  At  the  conclusion  of  the  experiment, 
wash  the  material  into  a  wide-mouthed  bottle,  fill  up  with 
distilled  water,  cork  and  shake  well,  let  it  stand  until 
clear  and  then  carefully  pour  away  the  liquid,  add  more 
water,  cork  and  shake  well  again,  reserve  for  future  use. 
The  second  clear  solution  is  called  limewater,  Ca(OH)2, 
and  is  much  used  in  the  laboratory  and  household  as  a 
mild  alkali,  try  it  with  litmus  paper,  also  taste  the 
clear  liquid. 

n.  Take  a  tablespoonful  of  common  plaster,  mix  this 
with  half  the  volume  of  water  in  a  porcelain  dish,  stir- 
ring as  before  with  a  thermometer,  record  the  result  and 
compare  with  experiment  10. 

12.  Slowly  pour  about  10  cc.  of  strong  sulphuric  acid, 
H2SO4 — into  50  cc.  of  cold  water,  stir  well  with  a  ther- 
mometer and  from  time  to  time  record  the  temperature. 

13.  Carefully  mix  exactly  9  volumes,  (45  cc.)  of  alco- 
hol, C2H5OH,  and  i  volume   (5  cc.)   of  water.     How 
many   volumes   result?     Use  the  burette  and   cylinder. 
Record  and  explain. 

14.  Effects  of  Filtration. — Add  a  few  drops  (10)  of 
the  liquid  from  experiment  5  to  a  large  volume  of  water, 


WATER  45 

(50  cc.),  filter  and  taste  the  liquid.  Is  any  change  pro- 
duced? Now  add  to  the  filtrate  a  few  drops  of  silver 
nitrate,  AgNO3,  shake  well  and  filter  again,  note  any 
difference. 

15.  Dissolve  a  few  grams   (1-2)   of  copper  sulphate 
in  250  cc.  of  water;  enough  should  be  used  to  give  the 
resulting  liquid   a  distinct  but  not  deep  shade.     Filter 
a  little  of  this,  what  is  the  result?     Reserve  the  bulk  for 
experiment  18.     What  inference  do  you  draw  from  ex- 
periments 14  and  15. 

1 6.  Charcoal    Filtration. — To    50    cc.    of  water    add 
enough  caramel  solution  to  give  it  a  distinct  but  not  deep 
yellow  color,  then  divide  into  two  equal  parts.     Filter 
one  through  dry  freshly  ignited  bone-black  several  times 
and  compare  the  color  of  the  resulting  liquid  with  the 
original  solution. 

17.  Effect  of  Alum. — Take  any  sample  of  cloudy  or 
slightly  colored  water,   even   soapy  water  will  answer. 
Add  a  very  small  quantity  of  finely  powdered  alum,  shake 
well,  filter  and  compare  with  the  original  sample. 

Water  should  be  neutral  or  slightly  alkaline  to  work 
well  with  alum. 

1 8.  Distillation  of  Water. — Place  on  a    wire    gauze 
or  sand-bath  and  make  firm  with  a  clamp,  a  round  bot- 
tom  half   liter   flask   containing   about   250   cc.   of   the 
liquid  made  in  experiment  15.     Insert  in  the  flask  a  cork 


46  HOUSEHOLD    CHEMISTRY 

fitted  with  a  thermometer  iand  45  degree  exit  tube, 
and  connect  this  latter  with  a  straight  tube  air  con- 
denser three  feet  long.  Boil  the  liquid  slowly,  taking 
note  of  the  boiling-point  of  the  liquid.  Carefully  ex- 
amine the  distillate,  see  if  you  can  detect  any  traces 
of  the  CuSO4,  if  so  moderate  the  heat,  collect  another 
portion  and  test  it  for  acidity.  Was  the  original  liquid 
acid?  Explain.  Remove  the  burner,  cool  the  apparatus 
and  add  5  cc.  of  ammonia,  shaking  well  after  adding 
the  alkali,  a  deep  blue  color  should  be  obtained.  Dis- 
till this  liquid  and  test  the  distillate  as  before. 

WATER  ANALYSIS 

Qualitative  Examination  of  Water. — No  attempt  will 
be  made  in  this  work  to  give  methods  for  quantitative 
estimation  of  the  impurities  found  in  water.  We  wish, 
however,  to  give  certain  qualitative  tests  which  will 
aid  in  detecting  such  impurities,  when  present  in  ab- 
normal amounts;  it  is  only  when  found  in  abnormal 
amounts  that  the  water  is  open  to  suspicion.  The  im- 
purities are  for  the  most  part  harmless  in  themselves. 
A  thorough  investigation  of  the  surroundings  and  of  the 
sources  of  contamination  of  the  water  supply,  care  in 
taking  the  sample,  and  other  precautions  are  quite  es- 
sential. 

The  tests  usually  made  are — color  and  appearance,  odor 
and  taste,  and  for  the  presence  of  total  solids,  free  and 


WATER  47 

albuminoid  ammonia,  nitrogen  as  nitrites  and  nitrates, 
chlorine,  temporary  and  permanent  hardness,  and  some- 
times phosphates,  sulphates,  etc. 

Total  Solids. — Evaporate  to  dryness  in  a  clean  porcelain 
dish  loo  cc.  of  ordinary  drinking  water.  Examine  the 
residue,  if  any,  and  notice  if  it  blackens  on  heating. 
This  indicates  organic  matter.  Phosphates  may  be  de- 
termined at  this  point  by  dissolving  the  residue  in  a 
little  hot  water,  and  adding  the  solution  to  a  mixture  of 
nitric  acid  and  ammonium  molybdate;  if  phosphates  are 
present,  a  yellow  color  or  crystalline  precipitate  will  be 
formed  on  gentle  heating. 

Ammonia. — Two  forms  of  ammonia  are  looked  for  in 
water,  the  "free  ammonia"  and  the  so-called  "albuminoid 
ammonia/' 

Free  Ammonia. — This  is  determined  by  distillation  as 
in  experiment  18,  omitting  the  copper  sulphate,  and  test- 
ing each  20  cc.  of  the  distillate  with  Nessler's  solution; 
which  gives  a  yellow  or  brown  color  in  the  presence  of 
ammonia.  Continue  until  a  portion  is  found  which  fails 
to  respond  to  the  test;  at  this  point  the  water  is  am- 
monia free. 

Albuminoid  Ammonia. — This  is  ammonia  derived  from 
organic  matter,  by  means  of  alkaline  permanganate  of 
potassium.  It  may  be  applied  to  the  water  already  in 
the  flask  from  which  the  free  ammonia  has  been  ex- 
pelled. 


48  HOUSEHOLD    CHEMISTRY 

Test. — Add  to  the  water  in  the  distillation  flask  20  cc. 
of  alkaline  potassium  permanganate,  and  test  the  distil- 
lates as  before  with  Nessler's  solution.  Note  the  differ- 
ence in  the  amount  of  ammonia  set  free. 

Nitrites. — The  presence  of  nitrites  in  water  is  sup- 
posed to  be  due  either  to  the  reduction  of  nitrates  al- 
ready present  in  the  water  by  the  action  of  organic  mat- 
ter, or  to  the  oxidation  of  organic  nitrogen  to  nitrite. 

Test. — To  about  100  cc.  of  water  in  a  Nessler  tube, 
add  5  cc.  of  a  freshly  prepared  mixture  of  equal  parts 
of  sulphanilic  acid  dissolved  in  acetic  acid  and  naphthyl- 
amine  acetate  dissolved  in  dilute  acetic  acid,  mix  and 
allow  to  stand  for  thirty  minutes.  If  the  solution  be- 
comes pink  the  water  contains  nitrites.  Compare  with 
water  known  to  be  nitrite  free. 

Chlorine. — Chlorine  is  found  mostly  as  sodium  chloride, 
although  other  chlorides  may  be  present. 

Test. — Place  in  a  small  casserole  or  porcelain  dish 
about  100  cc.  of  the  water  to  be  tested,  and  in  another 
dish  the  same  amount  of  distilled  water.  Add  to  each, 
two  or  three  drops  of  potassium  chromate  solution,  then 
add  drop  by  drop  a  dilute  solution  of  silver  nitrate 
(N/io)  stirring  after  each  drop  until  a  faint  tinge  of 
red  remains.  Obtain  the  same  tint  in  each,  and  note  the 
number  of  drops  of  silver  nitrate  used  in  each  case. 
The  difference  between  the  two  shows  the  amount  of 


WATER  49 

chloride  present.  (Each  drop  of  silver  nitrate  solution 
is  equivalent  to  0.000293  gram  sodium  chloride).  Ex- 
cess of  chlorides  usually  indicates  sewage  contamination. 

Oxygen  Consuming  Power. — Generally  ascribed  to  or- 
ganic matter. 

Fill  two  clean  eight  inch  test-tubes,  one  with  the  water 
to  be  tested,  the  other  with  distilled  water,  add  to  each 
the  same  amount  of  acidified  potassium  permanganate 
solution.  Be  careful  not  to  obtain  too  deep  a  shade 
and  see  that  the  shades  match.  On  standing  ten  min- 
utes, there  should  be  an  appreciable  lightening  in  color, 
greatest  in  the  tube  of  water  under  test.  If  the  color 
entirely  disappears,  the  amount  of  organic  matter  is  prob- 
ably dangerously  great.  Compare  with  the  test  under 
total  solids. 

Hardness. — By  hardness  is  meant  the  soap  destroying 
capacity  of  a  water.  This  property  is  due  principally  to 
the  fact  that  calcium  and  magnesium  salts  form,  with 
ordinary  soaps,  insoluble  compounds  or  soaps  which 
separate  as  a  curd  in  the  water  and  have  no  detergent 
value.  The  hardness  of  a  water  may  be  classified  under 
two  heads,  viz.,  "Temporary"  and  "Permanent." 

Temporary  Hardness. — Temporary  hardness  is  caused 
by  the  carbonates  of  calcium  and  magnesium  held  in 
solution  as  bicarbonates  by  carbonic  acid  present  in  the 


50  HOUSEHOLD    CHEMISTRY 

water.     Boiling  expels  the  CO2  causing  a  precipitation 
of  calcium  and  magnesium  carbonates. 

Test. — Place  100  cc.  of  the  water  to  be  tested  in  an 
eight  ounce  bottle,  add  an  alcoholic  solution  of  pure  cas- 
tile  soap  one-half  cc.  at  a  time,  shaking  thoroughly  after 
each  addition,  until  a  lather  is  formed  which  lasts  five 
minutes.  Note  the  amount  of  soap  solution  used. 

Now  boil  loo  cc.  of  the  sample,  cool  and  repeat  the 
test,  noting  again  the  amount  of  soap  solution  used. 
The  difference  gives  the  temporary  hardness. 

Permanent  Hardness. — Permanent  hardness  is  due  to 
the  presence  of  calcium  sulphate  and  other  soluble  salts 
of  calcium  and  magnesium,  not  carbonates,  held  in  solu- 
tion by  the  solvent  action  of  the  water  itself.  Such 
a  water  cannot  be  materially  softened  by  boiling  but  may 
be  softened  by  boiling  with  sodium  carbonate,  which 
converts  the  sulphates,  etc.,  into  carbonates  and  pre- 
cipitates them  as  such. 

Experiment  1. — Prepare  hard  water  by  dissolving  o.ioo 
grams  of  plaster  (calcium  sulphate)  in  500  cc.  of  dis- 
tilled water.  Pass  a  rapid  current  of  carbon  dioxide 
through  the  solution  and  continue,  at  least  as  long  as  in 
the  case  of  limewater  (page  33).  Why  is  the  action  not 
the  same?  Finally  add  sodium  carbonate  solution  and 
note  the  result.  Explain. 

Most  waters  possess  both  temporary  and  permanent 


WATER  51 

hardness,  in  which  case  the  total  hardness  is  first  deter- 
mined. The  water  is  then  boiled  and  the  permanent 
hardness  determined,  the  temporary  hardness  being  ob- 
tained by  difference. 


Chapter  V 

THE  METALS  AND  ALLOYS 

Only  those  in  common  use  will  be  considered. 

The  list  includes: 

Iron,  in  the  form  of  wrought  and  cast  iron  and  steel. 

Zinc,  rolled  or  sheet  and  cast. 

Copper. 

Lead,  as  sheet  or  pipe. 

Aluminium,  cast  and  rolled. 

Nickel — Also  various   compound   forms,   as    follows: 
Tin  plate,  thin  sheet  iron  or  steel  coated  with  molten 
tin. 

Galvanized  iron,  cast  or  wrought  iron  or  steel  coated 
with  molten  zinc. 

The  alloys  are  solid  solutions  of  metals  and  consti- 
tute a  valuable  member  of  this  group.  Generally  speak- 
ing, their  properties  are  similar  to  that  constituent  which 
forms  the  larger  part  of  the  mass,  but  they  are  usually 
harder  and  have  a  lower  melting-point. 

Familiar  alloys  of  silver  are  "sterling"  and  "coin ;"  of 
copper,  brass,  bronze,  and  German  silver ;  of  lead,  solder ; 
of  tin  pewter,  and  Brittania  metal.  All  the  metals  and 
alloys  are  subject  to  oxidation  or  rusting  in  the  presence 
or  air,  moisture  and  carbon  dioxide,  but  with  the  ex- 


THE  METALS  AND  ALLOYS  53 

ception  of  iron,  the  action  is  superficial  and  not  progres- 
sive, the  coat  of  oxide  protecting  the  metal  beneath  from 
further  action. 

Iron,  (Ferrum)  Fe,  occurs  in  nature  largely  in  the 
form  of  oxides;  haematite,  Fe2O3,  (red),  and  magne- 
tite, Fe3O4,  (black),  the  latter  possessing  magnetic  quali- 
ties and  commonly  called  "Lodestone." 

The  metal  is  obtained  by  fusing  the  ore  in  shaft  fur- 
naces with  excess  of  carbon  and  enough  limestone  to 
furnish  a  fusible  ash  or  slag  with  the  silicious  matter 
present  in  the  ore.  The  following  equations  explain  the 
reduction  and  slagging. 

2Fe304+8CO=3Fe2+8C02. 
SiO2+CaO=CaSiO3. 

The  product  "Pig  Iron,"  or  crude  cast  iron,  contains 
from  3-4  per  cent,  of  carbon  as  graphite  and  combined 
carbon  or  carbide  of  iron  Fe3C,  rendering  the  mass  fusi- 
ble. By  careful  smelting  in  small  shaft  furnaces  called 
"Cupolas,"  the  pig  iron  is  obtained  in  the  form  of  gray, 
white  and  mottled  iron,  depending  on  the  rapidity  of  cool- 
ing the  moulds.  Pig  iron  frequently  contains  small 
amounts  of  impurities,  sulphur  and  phosphorus,  render- 
ing the  product  short  or  brittle,  while  hot  or  cold; 
during  the  refining  process  these  are  almost  entirely 
removed  in  the  slag.  Cast  iron  is  brittle  and  hard,  it 
melts  without  softening  at  1200°  C.  and  yields  a  thin 


54  HOUSEHOLD    CHEMISTRY 

liquid  which  may  be  cast  in  sand  moulds.  The  quality 
of  the  product  depends  largely  on  the  purity  of  the  iron, 
(freedom  from  S.  and  P.),  its  temperature  of  cooling, 
and  the  smoothness  of  the  mould.  If  cast  iron  be  sub- 
sequently and  repeatedly  heated  to  redness  in  presence 
of  air,  it  becomes  much  harder  and  more  brittle,  fre- 
quently cracking  under  careless  handling  as  in  over- 
heated stove  lids,  etc. 

Cast  iron  heats  more  slowly  but  retains  its  heat  better 
than  other  forms  of  the  metal,  hence  its  use  for  oven 
plates,  sadirons,  stove  lids,  etc.  It  does  not  oxidize  as 
easily  as  steel  or  wrought  iron. 

Malleable  iron  is  a  form  of  cast  iron  which  has  been 
slowly  cooled  and  thereby  has  gained  a  certain  degree  of 
elasticity.  It  is  softer  and  less  brittle  than  ordinary  cast 
iron  and  is  much  used  in  house  hardware. 

Wrought  iron  and  steel  are  prepared  from  pig  iron 
by  burning  out  part  of  the  carbon  in  hot  air  furnaces  of 
special  construction. 

The  reverberatory  furnace  for  producing  wrought  iron 
is  really  a  large  oven  heated  by  gas  and  provided  with 
a  powerful  blast  of  hot  air.  Liquid  pig  iron  is  run  on  to 
the  hot  furnace  bed  where  the  excess  of  oxygen  removes 
the  carbon  as  follows:  C2+O2— 2CO.  As  the  CO  es- 
capes from  the  liquid  mass  it  produces  a  bubbling  like 
any  boiling  liquid.  Gradually  as  the  carbon  is  burned 


THE;  METALS  AND  ALLOYS  55 

out,  the  iron  becomes  pasty  or  semi-solid  and  is  collected 
in  balls  with  large  pokers  operated  by  hand  (puddling). 
When  the  balls  are  of  sufficient  size  they  are  removed 
with  large  tongs,  squeezed  to  remove  slag  and  rolled  into 
short  bars  (blooms  or  billets).  The  blooms  are  then 
reheated  until  soft  and  rolled  in  bars  and  rods;  when 
cold  the  bars  may  be  drawn  down  through  steel  dies  into 
wire  of  almost  any  degree  of  fineness.  The  bars  are  cold 
forged  into  nails  and  tacks.  Piano  wire,  the  purest  form 
of  iron,  contains  99.7  per  cent.  Fe,  the  balance  is  mainly 
carbon.  Cold  wrought  iron  is  quite  soft,  bends  easily  and 
has  great  tensile  strength.  It  does  not  melt  readily 
(1600°  C.)  but  softens  on  heating  and  may  be  forged 
and  welded. 

Steel  is  a  form  of  iron  between  cast  and  wrought, 
containing  1.5  per  cent,  carbon.  When  heated  and  slowly 
cooled  it  is  soft,  (mild)  but  if  suddenly  cooled  is  harder 
than  glass.  Hardened  steel  cautiously  reheated,  may  be 
softened  to  any  desired  extent.  (Tempering.)  At  a  high 
temperature  steel  melts  and  may  be  cast  like  iron. 

Two  kinds  of  steel  are  manufactured,  i.  e.,  Bessemer, 
the  cheaper  variety  used  for  rails,  plate  for  making  so- 
called  sheet  tin  and  galvanized  iron,  wire  nails,  etc., 
and  open  hearth  steel,  a  more  expensive  variety  used 
for  cutlery  and  tools. 

Bessemer  Process. — The  cast  iron  is  first  melted  in  a 
cupola,  and  then  run  into  a  special  furnace  (the  Con- 


56  HOUSEHOLD    CHEMISTRY 

verter),  where  a  powerful  blast  of  hot  air  bubbles 
through  the  molten  liquid  and  quickly  (15  minutes)  burns 
out  the  carbon  and  other  impurities  and  even  produces 
some  oxide.  Just  at  this  point,  a  small  portion  of  molten 
cast  iron  containing  manganese  and  the  proper  amount 
of  carbon  is  added  and  the  mixture  immediately  poured 
into  the  moulds  and  cooled.  The  function  of  the  man- 
ganese is  to  assist  in  holding  the  carbon  in  solution. 

Open  Hearth  Method. — The  cast  iron  is  melted  in  a  gas 
furnace  with  dish-shaped  bed  together  with  scrap  wrought 
iron  and  iron  ore.  After  eight  or  ten  hours  heating,  the 
operation  is  complete  and  the  liquid  steel  is  drawn  off 
and  cast  in  ingots. 

Steel  rusts  much  more  readily  than  cast  iron  and 
usually  needs,  especially  if  polished,  a  protecting  coat 
of  oil.  Rust  may  be  removed  by  soaking  in  kerosene  and 
rubbing  with  fine  emery  or  carborundum  and  oil. 

Rusting  of  Iron. — Two  forms  of  oxide  may  be  pro- 
duced, one  of  the  common  red  or  brown  rust,  FeO, 
Fe2O;{-{-H.>O  forms  in  the  air  in  presence  of  moisture 
and  CO2.  It  is  soft  and  friable  and  does  not  protect 
the  metal  from  further  action.  It  is  slightly  soluble 
in  water,  giving  it  a  characteristic  taste,  experienced 
in  drinking  water  conducted  by  iron  pipes.  The  other 
type  of  oxide,  Fe3O4,  is  formed  by  the  oxidation  of  hot 
iron,  (Russia  Iron),  or  by  the  action  of  superheated 
steam  and  carbon  monoxide  (Barff  Process),  Fe3O4 


THE  METALS  AND  ALLOYS  57 

forms  a  dark  gray  adherent  but  brittle  coat  and  protects 
the  metal  from  further  action. 

EXPERIMENTS  ON  IRONS  AND  STEEI 

Physical  Properties. — Notice  their  magnetic  qualities 
using  an  ordinary  horse-shoe  magnet  and  some  coarse 
needles,  pieces  of  soft  iron  wire  and  cast  iron. 

Heat  small  pieces  of  the  various  kinds  of  iron  in  the 
Bunsen  flame  and  note  their  behavior,  (time  of  heat- 
ing and  cooling). 

Temper  and  draw  temper  of  a  knitting  needle. 

Test  the  hardness  of  a  file  on  glass.  Break  off  one 
end  of  a  small  round  file  and  examine  the  fracture  with  a 
strong  lens. 

Chemical  Properties. — Boil  small  pieces  of  bright  iron 
(wire  or  cast)  in  the  following  liquids:  Dilute  mineral 
acid,  organic  acid  (acetic  and  tartaric)  and  caustic  soda. 
Record  the  results.  Filter  off  the  liquid  in  each  test  and 
make  it  acid  with  HC1  and  add  NH4CNS.  A  blood  red 
color  shows  iron  in  solution.  Treat  rusty  iron  in  the 
same  way  and  record  results.  Expose  small  pieces  of 
bright  iron  in  two  separate  bottles,  one  containing  a 
small  amount  of  water  and  the  other  water  and  carbon 
dioxide.  Cork  both  and  set  aside.  Which  rusts  first, 
why? 

Nickel,  a  hard  silver  white  metal  only  slightly  sus- 
ceptible to  oxidation  in  moist  air,  is  largely  used  as  a 


58  HOUSEHOLD    CHEMISTRY 

protective  and  decorative  coating  in  iron  and  copper. 
Pure  nickel  utensils  are  used  in  the  laboratory,  taking 
the  place  of  iron,  but  comparative  high  cost  has  pre- 
vented their  employment  in  the  house.  As  an  ingred- 
ient of  alloys,  nickel  is  found  in  German  silver  and  coin 
nickel. 

The  process  of  plating  is  as  follows :  Prepare  an 
ammoniacal  bath  of  ammonium  nickel  sulphate,  suspend 
in  it  the  article  to  be  plated  which  must  be  thoroughly 
cleaned  by  dipping  in  acid,  brushing  and  rinsing  in  water. 
This  forms  the  cathode  and  a  nickel  plate  the  anode. 

Nickel  plated  articles  should  always  be  cleaned  with 
a  mixture  of  diluted  ammonia  and  whiting,  or  rouge, 
and  polished  with  soft  cotton  waste. 

Experiment. — Heat  small  pieces  of  pure  nickel  with 
dilute  acids  and  alkalies  as  under  iron  and  record  the  re- 
sults. See  page  57.  Soluble  salts  of  nickel  have  a  green 
color  and  yield  a  black  precipitate  NiS  with  ammonium 
sulphide. 

Aluminium  (incorrectly  aluminum)  the  most  abundant 
of  the  metals,  a  constituent  of  common  minerals ;  Feld- 
spars, micas,  clays  and  cryolite.  The  metal  is  prepared 
by  electrolysis  of  the  oxide  in  a  bath  of  molten  cryolite. 

Aluminiumjs  silver-white  in  color,  almost  as  hard  and 
tenacious  as  steel,  melts  at  600-700°  C.  and  does  not  tar- 
nish readily.  On  account  of  its  lightness  it  is  much 
in  demand  for  cooking  utensils  but  care  must  be  taken 


METALS  AND  ALLOYS  59 

that  it  does  not  come  into  contact  with  acids  and  caustic 
alkalies,  which  vigorously  attack  it,  liberating  hydro- 
gen and  forming  soluble  aluminium  compounds. 

Experiment. — Heat  several  strips  of  thin  sheet  alu- 
minium in  a  large  test-tube  with  10  per  cent,  caustic 
soda  solution.  Note  the  violent  effervescence;  approach 
a  lighted  match  to  the  mouth  of  the  tube.  What  hap- 
pens? Explain.  Before  the  metal  has  entirely  disap- 
peared, cool  the  tube,  add  an  equal  bulk  of  water,  filter 
the  liquid  and  exactly  neutralize  the  filtrate  with  dilute 
HC1.  Note  the  copious  flocculent  precipitate,  A12(OH)6. 
Repeat  the  experiment  using  HC1  instead  of  alkali  and 
finally  neutralizing  with  ammonia.  Write  equations  ex- 
planatory of  the  chemical  changes  observed. 

Aluminium  articles  should  never  be  washed  with  strong 
acids  or  alkalies,  rather  use  neutral  soap  with  a  small 
addition  of  ammonia  and  polish  with  some  smooth  pow- 
der such  as  whiting  or  rouge.  Powdered  aluminium 
mixed  with  oxidized  linseed  oil  and  amyl  acetate  or  ace- 
tone is  largely  used  as  a  bronze  paint. 

Two  alloys  are  known;  magnalium,  containing  6-30 
per  cent,  of  magnesium,  taking  a  high  polish  and  work- 
ing well  in  the  lathe,  and  aluminium  bronze,  88-95  Per 
cent,  of  copper,  easily  fusible,  golden  in  color  and  of 
great  strength  and  resisting  qualities. 

Zinc  occurs  chiefly  as  Calamine  or  Zinc  blende  ZnCO3. 
After  calculation  to  drive  off  CO2,  the  oxide  is  mixed 
5 


6O  HOUSEHOLD    CHEMISTRY 

with  carbon  and  distilled  in  earthen  retorts  at  1300- 
1400°  C. ;  crude  metallic  zinc  "spelter"  condenses  in  the 
receivers  and  CO  burns  at  a  small  opening. 

ZnCO3=ZnO-{-CO2. 

2ZnO+C2=2Zn+2CO. 

Zinc  is  bluish  white,  highly  crystalline  and  brittle 
when  cold.  By  heating  to  120-150°  C.  and  rolling  tinder 
hot  rolls  it  remains  pliable  and  soft  on  cooling  (sheet 
zinc).  At  200-300°  C.  it  becomes  brittle  again,  melts 
at  433°  C.  and  boils  at  920°  C. 

Zinc  burns  in  the  air  with  a  bluish  white  flame  yielding 
a  white  oxide  (used  as  a  base  for  paint). 

In  moist  air,  it  oxidized  and  absorbs  CO2,  forming  a 
thin  adherent  coat  of  basic  carbonate  which  protects  the 
metal  from  further  change.  Dilute  acids  readily  dis- 
solve this  coating  and  thus  restore  the  original  brilliancy. 
Acids  and  alkalies  freely  attack  zinc,  liberating  hydrogen 
and  producing  soluble  compounds  which  are  poisonous, 
hence  zinc  vessels  should  never  be  used  for  the  prepara- 
tion or  storage  of  food. 

Sheet  zinc  is  frequently  used  for  roofs,  gutters,  cor- 
nices and  leaders  of  buildings ;  but  does  not  last  well 
near  the  seashore,  on  account  of  the  salt  in  the  atmos- 
phere. 

The  molten  metal  mixes  in  all  proportions  with  cop- 
per, tin  and  antimony,  see  German  silver,  brass,  etc. 


THE  METALS  AND  ALLOYS  6l 

Zinc,  both  cast  and  rolled,  is  largely  used  in  primary 
batteries.  It  lasts  much  better  if  cleaned  with  dilute 
sulphuric  acid  and  coated  with  mercury  (amalgamated). 
Do  not  attempt  to  cleanse  zinc  or  galvanized  iron  with 
anything  but  neutral  soap  and  hot  water. 

Experiment  1. — Immerse  strips  of  sheet  zinc  in  a  dilute 
solution  of  sodium  chloride  for  several  days,  finally  re- 
move and  examine  the  strips  for  corrosion  and  test  the 
liquid  with  hydrogen  sulphide  for  soluble  zinc.  The 
action  will  be  much  more  apparent  if  clean  iron  or  cop- 
per nails  are  in  contact  with  the  zinc. 

Experiment  2. — All  kinds  of  iron  are  galvanized  or 
coated  with  zinc  by  first  cleansing  the  article  thoroughly 
with  acid,  draining  and  then  dipping  in  molten  zinc. 
Try  it. 

Experiment  3. — Treat  small  pieces  of  sheet  zinc  with 
dilute  acids  and  alkalies,  see  experiments  on  iron,  page 
57  and  record  the  results. 

Copper,  Silver  and  Gold. — Copper,  cuprum,1  Cu,  is  found 
native,  also  as  sulphide  and  carbonate.  Native  copper  ore 
is  crushed,  washed  to  remove  rock  and  melted  with  flux. 
The  metal  usually  contains  a  small  amount  of  silver  which 
is  removed  by  electrolysis.  Carbonates  and  oxides  are 
fused  with  coal  to  reduce  the  metal.  Sulphide  ores  re- 

1  The  term  "Cuprum"  was  derived  from  the  island  of  Cyprus 
in  the  Mediterranean,  where  copper  was  first  mined  and  extracted. 


62  HOUSEHOLD    CHEMISTRY 

quire  complex  treatment ;  in  Montana  the  procedure  is  as 
follows:  Partial  oxidation  by  roasting  and  subsequent 
fusion  in  Bessemer  converter  (with  silicious  lining) 
sand  and  air  are  blown  through  the  molten  mass.  The 
iron  is  oxidized  and  combines  with  silica  forming  a  slag 
which  floats  on  the  copper.  Sulphur,  arsenic  and  lead 
are  oxidized  and  volatilized. 

Copper  is  refined  by  electrolysis  in  the  following  man- 
ner: thin  copper  sheets  coated  with  graphite  are  sus- 
pended in  tanks  of  copper  sulphate  solution  and  con- 
nected with  the  negative  pole  of  the  dynamo,  opposite 
are  heavy  plates  of  crude  copper  connected  with  the  posi- 
tive pole.  Pure  copper  is  deposited  on  the  cathode, 
while  the  SO4  ionizes  the  anode.  The  impurities  not 
ionized  fall  to  the  bottom  of  the  tank. 

Physical  Properties. — Copper  is  a  red  metal  melting 
at  1057°  C.  and  is  a  good  conductor  of  heat  and  elec- 
tricity; it  is  very  malleable  and  ductile. 

Chemical  Properties. — Copper  slowly  oxidizes  in  dry 
air  forming  Cu2O  and  in  moist  air  green  basic  carbonate 
(not  verdigris).  It  resists  the  action  of  cold  dilute 
acids  and  alkalies  and  is  much  in  demand  for  the  manu- 
facture of  apparatus  used  in  food  preparation,  i.e.,  vac- 
uum pan  for  sugar,  milk,  etc.,  apparatus  for  canning 
and  preserving,  candy  making,  beer  brewing,  etc.  Large 
hotels  and  restaurants  use  copper  cooking  utensils. 

The  most  important  alloys  of  copper  are : 


THE  METALS  AND  ALLOYS  63 

Brass  containing 18-40^0  Zn, 

Bronze  containing 11$  Zn,  3-8%  Sn,  some  Pb, 

Gun  metal  containing 10%  Sn, 

Bell  metal  containing 25  %  Sn, 

German  silver  containing 19-44%  Zn,  6-22%  Ni. 

Metallic  copper  its  alloys  are  readily  cleaned  with 
dilute  oxalic  acid  or  ammonia. 

Experiment  1. — Hold  a  small  spiral  of  copper  wire  in 
the  upper  part  of  the  Bunsen  flame  until  it  glows,  then 
immediately  drop  it  into  a  test-tube  of  methyl  alcohol. 
After  the  first  violent  action  is  over  pour  out  the  liquid 
and  observe  its  odor ;  of  what  does  it  remind  you  ?  Ex- 
amine the  wire  spiral,  note  its  brilliancy  and  color.  It 
is  clean  copper. 

Experiment  2. — Heat  small  pieces  of  clean  and  tar- 
nished copper  separately  in  the  following  liquids:  dilute 
HC1,  dilute  acetic  acid,  10  per  cent,  caustic  soda,  dilute 
ammonia.  Finally  pour  off  the  liquids  and  add  to  each  an 
excess  of  ammonia,  a  blue  color  shows  the  presence  of 
copper.  Have  the  pieces  of  copper  been  visibly  affect- 
ed? 

Experiment  3. — Grasp  a  short  piece  of  stout  copper 
wire  in  the  fingers  and  hold  the  other  end  in  the  Bunsen 
flame,  what  happens,  has  this  any  bearing  on  the  use 
of  copper  for  cooking  utensils? 

Experiment  4. — Expose  small  pieces  of  copper  in  wide- 
mouthed  bottles  containing  a  small  amount  of  carbonic 


64  HOUSEHOLD    CHEMISTRY 

acid  water,  keeping  them  covered  with  watch-glasses 
and  standing  in  a  cool  place.  Examine  the  greenish 
coating  on  the  copper  and  afterwards  dissolve  it  off  with 
dilute  acetic  acid  and  add  dilute  ammonia  to  the  solu- 
tion. Copper  utensils  are  often  coated  with  metallic 
tin  to  prevent  the  formation  of  the  green  coating  (basic 
carbonate  of  copper). 

Silver,  Ag,  Argentum  found  native  with  copper  and 
also  as  a  sulphide  chiefly  associated  with  lead  sulphide 
Galena;  native  silver  is  extracted  by  electrolysis  as  de- 
scribed under  copper.  Silver  is  separated  from  the 
lead  extracted  from  galena  (see  lead)  by  the  process  of 
zinc  desilverization  and  cupellation.  Zinc  and  lead  are 
quite  insoluble  in  each  other  and  silver  is  more  soluble 
in  zinc  than  is  lead,  taking  advantage  of  these  facts,  the 
process  is  operated  as  follows:  silver  lead  is  melted  in 
large  cast  iron  kettles  and  the  zinc  added  and  well  stirred. 
On  standing  and  partially  cooling  the  zinc  carrying  sil- 
ver and  a  little  lead,  rises  and  forms  a  crust  which  is 
skimmed  and  heated  in  retorts  to  drive  off  zinc.  The 
residue  Pb  -f-  Ag  is  then  heated  in  a  reverberatory  fur- 
nace with  bone  ash  bed.  The  lead  oxidizes,  melts  and  is 
absorbed  by  the  bone  ash  leaving  the  silver. 

In  Mexico,  the  "Patio"  process  is  used.  This  con- 
sists in  roasting  the  ores  and  treating  with  copper  chlo- 
rides to  produce  AgCl.  The  silver  chloride  is  reduced 
and  dissolved  with  mercury  forming  a  liquid  alloy  (amal- 


THE  METALS  AND  ALLOYS  65 

gam),  which  is  subsequently  distilled  to  free  it  from 
mercury. 

Silver  is  a  soft  white  metal,  highly  ductile  and  mallea- 
ble :  an  excellent  conductor  of  heat  and  electricity,  melts 
at  960°  C.  It  does  not  oxidize  readily  in  air  but  is  rapidly 
attacked  by  sulphides,  producing  Ag2S,  (black). 

In  order  to  harden  silver,  it  is  alloyed  with  copper  in 
the  following  proportions:  coin  silver,  900  parts  silver, 
loo  parts  copper.  Sterling  silver,  925  parts  silver,  75  parts 
copper.  All  solid  household  silver  is  now  "Sterling." 

Many  silver  ornaments  contain  even  less  silver  but 
articles  stamped  "sterling"  are  trustworthy.  Silver  plated- 
ware  consists  of  articles  fashioned  of  German  silver  or 
pewter,  on  which  is  deposited  by  electrolysis  a  triple  or 
quadruple  coating  of  pure  silver.  The  process  is  simi- 
lar to  copper  plating,  the  silver  bath  consisting  of  po- 
tassium silver  cyanide  KAg(CN)2.  The  coating  has  a 
frosted  appearance  and  needs  burnishing  or  smoothing 
before  use.  Since  the  coat  deposited  in  this  manner  is 
pure  silver,  these  articles  do  not  stand  as  much  careless 
and  rough  handling  as  the  harder  sterling  or  coin  ware, 
much  of  the  coating  is  rubbed  off  in  the  process  of  cleans- 
ing with  the  so-called  silver  polishes.  Plated  ware  will 
last  much  longer  if  simply  washed  with  hot  water  and 
neutral  soap.  In  order  to  remove  the  tarnish  due  to 
sulphides  (eggs),  soak  the  articles  in  a  clean  tin  dish 
pan  containing  enough  baking  soda  solution  to  cover  and 


66  HOUSEHOLD    CHEMISTRY 

let  them  remain  until  bright.  The  soda  solution  is  made 
by  dissolving  a  tablespoonful  of  NaHCO3  in  a  quart 
of  tepid  water.  Silver  is  insoluble  in  alkalies,  but  dis- 
solves readily  in  strong  mineral  acids,  particularly  nitric 
acid.  Oxidized  silver  is  prepared  by  dipping  the  ob- 
ject in  a  solution  of  hydrogen  potassium  sulphide  KHS 
until  sufficiently  blackened. 

Mirrors  of  metallic  silver  are  superior  to  any  others. 
They  may  be  made  as  follows :  add  to  a  weak  solution  of 
silver  nitrate  just  enough  ammonia  to  dissolve  the  pre- 
cipitate first  formed,  then  a  little  caustic  soda  and  finally 
a  little  more  ammonia  and  glycerine,  glucose,  formalde- 
hyde or  a  neutral  tartrate.  The  glass  article  to  be  sil- 
vered should  previously  be  cleaned  with  nitric  acid, 
water  and  strong  alcohol  in  the  order  mentioned.  The 
clean  object  is  now  immersed  in  the  liquid  and  gently 
heated  until  a  sufficient  coating  is  deposited.  Try  sil- 
vering a  convex  glass  or  large  test-tube  by  this  method. 

Tin,  (Stannum)  Sn,  occurs  in  Cornwall  and  the  East 
Indies  as  Cassiterite  (tin  stone)  SnO2.  The  ore  is 
crushed  and  washed  to  remove  rock,  roasted  to  oxidize 
sulphide  of  iron  and  copper  and  to  remove  arsenic,  then 
leached  with  water  to  dissolve  sulphate  of  iron  and  cop- 
per, dried  and  reduced  with  coal  in  a  reverberatory  fur- 
nace. Tin  is  a  soft  silver  white  crystalline  metal,  mallea- 
ble, but  not  ductile,  it  melts  at  233°  C.  On  bending  bar 


THE  METALS  AND  ALLOYS  67 

tin,  a  peculiar  crackling  sound  is  heard  called  the  "cry 
of  tin."  Tin  is  non-poisonous. 

Tin  plate  is  made  by  dipping  carefully  cleaned  sheets 
of  iron  or  steel  in  molten  tin.  It  is  much  used  for  roof- 
ing, household  ware  and  cans  for  preserving  food.  Care 
must  always  be  exercised  that  tin  vessels  are  not  over 
heated  since  the  element  has  a  low  fusion  point  and  will 
run  off  leaving  the  iron  bare,  therefore  it  should  never 
be  used  in  the  oven  or  for  broiling,  roasting  or  frying. 
Liquid  mixtures  may  be  cooked  in  tin  vessels  without 
doing  any  damage. 

Various  useful  alloys  are  known,  viz.,  bronze,  soft 
solder  (half  tin,  half  lead)  pewter  25  per  cent,  lead, 
Britannia  metal  10  per  cent,  antimony. 

Experiment  1. — Heat  a  small  piece  of  tin  plate  over  the 
Bunsen  flame,  note  the  crystalline  appearance  on  cool- 
ing; treat  a  piece  with  moderately  strong  acid  and  note 
a  similar  effect.  Where  have  you  frequently  seen  this 
phenomenon  ? 

Experiment  2. — Scrape  some  tin  from  a  sheet  and  heat 
it  with  a  blowpipe  on  charcoal  before  the  oxidizing  flame, 
cool,  moisten  with  nitrate  of  cobalt  solution  and  heat 
again  strongly.  Note  the  dark  green  mass  on  cooling. 

Experiment  3. — Dissolve  tin  in  hot  strong  HC1,  cool 
and  add  a  little  mercuric  chloride  solution  to  the  liquid; 
observe  the  white  precipitate  turning  black. 


68  HOUSEHOLD    CHEMISTRY 

SnCl8+2HgCla=SnCl4+Hg2Cl2. 

Hg2Cl2+SnCl2=Hg2+SnCl4". 

Experiment  4. — Join  small  pieces  of  tin  by  "solder- 
ing" as  follows:  Heat  die  soldering  iron  (copper) 
slowly  in  the  Bunsen  flame.  While  heating  prepare  the 
tin  by  rubbing  with  a  dean  rag  and  sprinkling  with  rosin 
powder.  When  the  iron  is  hot,  wipe  it  gently  with  a 
cotton  rag  and  bring  it  directly  in  contact  with  the  tin 
at  the  joint,  at  the  same  time  touching  the  end  of  the  iron 
with  the  bar  of  solder.  A  little  of  the  solder  will  melt 
off  and  may  be  run  up  and  down  the  joint  until  it  is 
closed.  If  the  tin  is  rusty,  scrape  it  bright  and  touch 
with  a  solution  of  zinc  chloride ;  apply  hot  solder  and 
rub  with  the  hot  iron  until  the  spot  is  well  coated. 

Brass  and  copper  may  be  soldered  in  the  same  man- 
ner. In  order  to  do  good  work,  the  point  of  the  solder- 
ing iron  should  always  be  well  tinned.  This  is  done  by 
first  filing  the  hot  copper  or  rubbing  it  with  ammonium 
chloride,  immediately  afterward  with  rosin  powder  and 
solder. 

Tin  plate  for  roofs  and  gutters  frequently  contains 
much  lead. 

Lead,  Pb  (Plumbum)  occurs  principally  as  Galena,  PbS. 
(frequently  carrying  silver).  The  metal  is  obtained  by 
roasting  the  ore  until  partially  converted  into  oxide  and 
sulphate.  On  closing  the  furnace  doors  and  increasing 
the  heat,  the  charge  is  reduced  to  metal : 


THE  METALS  AND  ALLOYS  69 


PbS+PbSO4=2Pb+2SO2. 

Lead  is  gray  in  color,  soft,  of  slight  tensile  strength 
but  very  malleable.  Melting-point  326°  C.  It  is  only 
slightly  soluble  in  acids  and  alkalies.  Lead  pipes  are 
formed  by  forcing  warm  lead  through  steel  dies  by  hy- 
draulic pressure.  They  are  much  used  for  conducting 
water  in  the  household.  The  danger  of  drinking  water 
conducted  by  lead  pipes  is  much  exaggerated.  Unless 
the  water  is  unusually  soft,  the  interior  of  the  pipe  quick- 
ly becomes  coated  with  insoluble  sulphate  and  carbo- 
nate. A  wise  precaution  with  new  plumbing  is  to  allow 
the  water  to  run  for  some  minutes  before  use.  Lead 
enters  into  many  useful  alloys  previously  mentioned. 

Lead  oxidizes  superficially,  the  compound  formed  be- 
ing the  black  suboxide,  Pb2O,  formerly  used  in  place  of 
graphite  for  lead  pencils. 

Oxide  of  lead  is  very  soluble  in  acids  and  alkalies. 

Test  for  the  lead  with  bismuth  flux  on  charcoal  or 
plaster  plate. 

Experiment  1.  —  Hammer  a  small  piece  of  lead  into  a 
cube,  notice  how  easily  it  can  be  formed  in  any  shape 
(lack  of  cohesion).  Observe  the  soil  on  the  fingers. 

Experiment  2.  —  Heat  the  small  cube  prepared  in  the 
first  experiment  in  a  shallow  porcelain  or  iron  crucible, 
stirring  with  a  stout  iron  wire,  noting  the  rapidly  form- 


7O  HOUSEHOLD    CHEMISTRY 

ing  crust  of  PbO.     If  the  heat  is  not  carried  too  high, 
the  metal  will  all  turn  to  oxide  in  a  short  time. 

Experiment  3. — Divide  the  oxide  formed  in  Experi- 
ment 2  into  two  equal  parts.  Dissolve  one  in  dilute 
HNO3  and  the  other  in  acetic  acid ;  pour  a  little  of  each 
solution  in  two  separate  watch-glasses  and  set  them  aside 
to  evaporate.  Examine  the  crystalline  residue  in  each 
case.  Scrape  two  pieces  of  lead  bright  and  immerse 
one  in  strong  nitric  acid,  the  other  in  acetic  acid;  allow 
them  to  stand  several  days  and  then  examine. 

Experiment  4. — Immerse  bright  lead  in  carbonic  acid 
water;  after  several  hours  standing  pour  off  the  water 
and  test  with  hydrogen  sulphide. 

Treat  small  pieces  of  bright  and  tarnished  lead  sep- 
arately in  weak  solutions  of  acids  and  alkali.  Pour 
off  the  clear  solutions,  acidify  with  HNO3,  where  nec- 
essary, and  test  for  lead  by  passing  H2S  through  the 
liquid.  A  black  precipitate  (PbS)  indicates  lead. 

Each  student  should  make  a  tabular  statement  giving 
the  results  of  the  action  of  acids  and  alkali  on  the  fore- 
going metals. 


Chapter  VI 

ACIDS  AND  BASES   (ALKALIES) 

The  most  common  and  useful  acids  are: 

Hydrochloric  (HC1),  sulphuric  (H2SO4),  nitric 
(HNO3)  and  acetic  (CH3COOH). 

Hydrochloric  acid  (HC1)  is  the  saturated  solution 
of  the  gas,  HC1,  in  pure  water  under  N.  T.  P.  condi- 
tions. It  is  clear  colorless  liquid  with  pungent  odor 
and  strong  acid  taste,  sp.  gr.  1.2  and  contains  40  per 
cent,  of  the  gas. 

Hydrochloric  acid  is  an  excellent  solvent  for  metals 
and  insoluble  salts. 

On  heating,  the  concentrated  solution  gradually  loses 
gaseous  HC1  until  a  sp.  gr.  of  i.i  (20  per  cent.)  has  been 
reached;  the  balance  of  the  liquid  then  distills  of  con- 
stant composition. 

The  commercial  form  known  as  muriatic  acid  always 
contains  iron,  giving  yellow  color  to  the  solution,  but 
may  be  used  for  generating  H2S,  etc.  For  laboratory 
purposes,  the  acid  is  used  in  the  concentrated  form  sp. 
gr.  1.2  and  in  the  dilute  form  sp.  gr.  i.i ;  the  latter  is 
prepared  by  diluting  the  concentrated  acid  with  an  equal 
volume  of  distilled  water. 

Free  hydrochloric   acid  occurs   in  the  gastric  juice, 


72  HOUSEHOLD    CHEMISTRY 

the  solution  having  an  average  strength  of  0.2  per  cent. 
For  artificial  digestion  experiments,  this  liquid  is  pre- 
pared by  adding  6.5  cc.  of  the  concentrated  acid  to  one 
liter  of  distilled  water. 

Combined  hydrochloric  acid  may  be  identified  and  de- 
termined by  means  of  a  solution  of  silver  nitrate  with 
which  it  makes  a  curdy  white  precipitate,  soluble  in  am- 
monium hydroxide. 

Free  hydrochloric  acid  is  indicated  by  a  violet  or  pur- 
plish color  when  heated  with  a  weak  solution  of  egg  al- 
bumen (see  tests  on  proteins,  page  143).  A  more  delicate 
test  (Boas')  is  made  by  warming  a  few  drops  of  the 
liquid  with  several  cubic  centimeters  of  a  solution  of  I 
gram  of  resorcin  and  3  grams  of  sugar,  in  a  porcelain 
dish,  if  present  the  HC1  develops  a  red  color. 

Sulphuric  acid,  H2SO4,  (HO)2SO2,  a  heavy,  non- vola- 
tile, colorless,  viscous  liquid,  b.p./339  C,  sp.  gr.  1.84,  con- 
taining 96  per  cent.  H2SO4.  It  mixes  with  water  in  all 
proportions,  developing  great  heat  during  the  operation. 
Caution:  In  diluting,  always  pour  the  cold  acid  slow- 
ly into  cold  water  contained  in  a  beaker  or  thin  flask. 

On  account  of  its  strong  affinity  for  water,  the  acid 
is  an  excellent  drying  agent.  A  small  beaker  half 
filled  with  the  cone,  acid  exposed  in  the  balance  case 
keeps  the  atmosphere  dry  for  weeks;  for  the  same  rea- 
son it  is  used  in  desiccators.  The  concentrated  acid, 
especially  when  heated,  is  a  powerful  oxidizing  agent, 


ACIDS  AND  BASES    ( ALKALIES )  73 

splitting  into  H2O,  SO^  and  O  (Kjeldahl  Digestion). 
The  dilute  forms  acts  as  a  general  solvent  and  hydrolyz- 
ing  agent.  For  laboratory  purposes,  the  concentrated 
and  dilute  forms  sp.  gr.  i.i  (H2SO4  I  vol.,  water  7  vols.) 
are  used.  A  special  acid  (sp.  gr.  1.8)  is  employed  in  the 
Babcock  process  for  determining  fat  in  milk. 

Commercial  sulphuric  acid  or  oil  of  vitriol  has  a  sp. 
gr.  of  66°  Be.  It  is  brownish  in  color,  due  to  organic 
impurities  and  is  also  likely  to  contain  arsenic,  lead  and 
oxides  of  nitrogen.  This  form  of  acid  is  extensively  em- 
ployed in  manufacturing  chemistry,  in  the  production 
and  purification  of  hydrocarbons,  coal  tar  colors,  etc. 

Sulphuric  acid  forms  two  classes  of  salts,  normal  and 
acid  or  bi-salts,  according  as  both  or  one  hydrogen  are 
replaced. 

Combined  sulphuric  acid  (sulphates),  if  soluble  pre- 
cipitates a  solution  of  barium  chloride  forming  white 
crystalline  barium  sulphate  insoluble  in  acids.  Free  sul- 
phuric acid  carefully  evaporated  with  sugar  solution  over 
a  water-bath  chars  the  liquid. 

Nitric  acid  HNO3,  HONO2,  a  pungent  colorless  liquid 
sp.  gr.  1.42  (69  per  cent.)  soluble  in  water  in  all  propor- 
tions and  not  volatile  at  ordinary  temperatures. 

It  is  a  powerful  oxidizing  agent,  two  molecules  splitting 
into  H2O,  2NO,  30.  Forms  nitro  compounds  with  organic 
substances.  Ex.  nitrocellulose,  nitroglycerine,  combines 
with  protein  substances  forming  insoluble  yellow  com- 


74  HOUSEHOLD    CHEMISTRY 

pounds  (acid  stains  on  fingers  and  clothing).  It  is 
used  as  a  general  solvent,  but  unlike  other  acids  does  not 
yield  hydrogen  when  attacked  by  metals.  Concentrated 
and  dilute  forms  (HNO3  i  vol.,  H2O  2.  vols.,  sp.  gr.  i.i) 
are  useful  laboratory  reagents. 

Commercial  nitric  acid  is  known  as  Aqua  Fords.  It 
is  a  yellow  liquid,  sp.  gr.  1.37,  containing  oxides  of 
nitrogen  and  other  impurities. 

For  tests  on  free  and  combined  nitric  acid  see  experi- 
ment n.  There  is  much  misconception  concerning  the 
strength  of  the  above  mentioned  mineral  acids.  Ac- 
cording to  their  equivalents,  36.5  pts.  pure  HC1,  49  pts. 
of  H2SO4,  and  63  pts.  HNO3  neutralize  the  same  amount 
of  alkali — see  page  81,  Normal  Solutions. 

Acetic  acid,  HC2H3O2,  CH3COOH  is  a  colorless, 
strong  smelling,  sour  liquid  volatile  at  118°  C. 

The  usual  forms  are  the  50  per  cent,  and  the  glacial 
acid.  Acetic  acid  is  very  generally  used  as  a  solvent  in 
the  laboratory.  In  the  household,  a  5  per  cent,  solution 
containing  extractive  matter  is  known  as  vinegar.  The 
equivalent  of  acetic  acid  is  60. 

Commercial  acetic  acid,  a  product  of  wood  distillation 
is  largely  used  in  the  manufacture  of  white  lead,  pig- 
ments, dyes,  etc.  The  preparation  of  vinegar  is  due 
to  the  action  of  bacteria  "mother  of  vinegar"  on  dilute 
alcoholic  liquids,  beer,  light  wine,  cider,  etc.  The  change 
is  due  to  oxidation  and  can  only  take  place  in  the  pres- 


ACIDS  AND  BASES    (ALKAUES)  75 

ence  of  air.  In  the  old  fashioned  practice,  oak  casks 
lying  on  their  sides  in  cool  dark  cellars  were  half  filled 
with  the  alcoholic  liquid,  the  bungs  were  left  out  for 
free  access  of  air,  and  in  the  course  of  several  months 
the  liquid  soured.  From  time  to  time,  some  vinegar  was 
drawn  off  and  replaced  with  fresh  alcoholic  liquid. 

The  modern  method  known  as  the  "Quick"  vinegar 
process  is  operated  as  follows :  large  oak  casks  with 
perforated  bottoms  are  filled  with  beech  wood  shavings 
and  saturated  wtih  strong  cloudy  vinegar,  the  bacteria 
collect  on  the  shavings  and  when  the  alcoholic  liquid  is 
allowed  to  trickle  through  the  cask,  the  large  oxidizing 
surface  makes  the  action  rapid.  The  liquid  is  passed 
through  the  cask  several  times. 

Acetic  acid  forms  two  classes  of  salts,  metallic  and 
organic  or  ester;  it  is  monatomic. 

The  glacial  form  of  acid  produced  by  lowering  the 
temperature  until  the  acid  crystallizes,  is  used  as  a  de- 
hydrating agent.  Combined  acetic  acid  (metallic  base 
acetate)  is  identified  by  heating  with  a  mixture  of  sul- 
phuric acid  and  ethyl  alcohol  producing  ethyl  acetate 
(ester),  recognized  by  its  odor  (cider). 

1.  Experiments  on  the  Acids. — Dilute  10  cc.  of  cone. 
HC1  to  loo  with  distilled  water,  mix  well  and  place  in  a 
small  distilling  flask :  see  experiments  under  water.  Slow- 
ly distill  the  liquid  and  test  each  10  cc.  for  acidity. 

2.  Neutralize   10  cc.  of  carbonate  of  soda   solution 
6 


?6  HOUSEHOLD    CHEMISTRY 

with  HC1,  evaporate  the  liquid  to  dryness  in  a  porce- 
lain dish,  examine  the  product. 

3.  Test  the  solubility  of  marble,  gypsum,  iron  rust 
and  copper  in  hydrochloric  acid. 

4.  Add  concentrated  HC1  to  a  saturated  solution  of 
salt,  explain  the  phenomenon. 

5.  Place  37  cc.  of  cone.  H2SO4  in  a  50  cc.  flask,  add 
13  cc.  of  cold  water  and  mix  well.     On  cooling,  how 
many  cc.  of  water  must  be  added  to  bring  the  liquid 
to  the  mark? 

6.  Drop  a  crystal  of  CuSO4  into  cone.  H2SO4,  ex- 
plain what  happens. 

7.  Add  dilute  sulphuric  acid  to  solutions  of  barium 
chloride,  calcium  hydroxide,  lead  acetate  and  silver  ni- 
trate.    Explain  what  happens  in  each  case,  write  equa- 
tions. 

8.  Half  fill  two  test-tubes  (6  inch)  with  dilute  nitric 
acid,   add  pulverized  copper  oxide  to  one  and  a  strip 
of  clean  copper  foil  to  the  other.     Explain  the  differ- 
ence of  action,  write  equations. 

9.  Soak  a  small  piece  of  absorbent  cotton  for  some 
time  in  a  mixture  of  cone,  nitric  and  sulphuric  acids, 
take  out,  wash  and  dry;  is  it  soluble  in  alcohol  and 
ether?    Try  to  burn  another  piece,  what  happens? 

10.  Treat   small  pieces  of   sheet  zinc  with  hot  con- 
centrated HNO3  for  several  minutes,  cool,  add  excess 
of  NaOH.     What  gas  is  evolved,  explain? 


ACIDS  AND  BASES    (ALKALIES)  7/ 

11.  Thoroughly  moisten  starch  with  strong  HNO3. 
What  gas  is  evolved  during  the  action? 

12.  Pour  one  inch  of  cone.  H2SO4  into  a  large  test- 
tube,  add  carefully  a  solution  of  ferrous  sulphate  (do 
not  mix)  ;  cool  if  necessary,  and  add  very  dilute  nitric 
acid.     Note  the  brown  ring.     (Test  for  nitrates.) 

13.  Add  a  few  drops  of  strong  nitric  acid  to  some 
weak  albumen;  warm  gently  and  note  the  color  (yellow). 

14.  Plunge  pieces  of  bright  iron,  copper,  zinc  and 
lead  in  separate  test-tubes  containing  strong  acetic  acid. 
Is  there  any  action  after  standing  some  minutes?     Fin- 
ally blow  the  expired  breath,  by  means  of  a  glass  tube, 
through  the  tube  containing  the  copper,  what  happens? 

15.  Boil  about  100  cc.  of  ordinary  5  per  cent,  acetic 
acid  in  a  beaker  and  from  time  to  time  test  the  vapor 
with  blue  litmus  paper,  when  the  liquid  is  low  add  hot 
water  and  boil  again,  test  as  before.     Can  you  drive  off 
all  the  acid  at  the  boiling-point  (212°  F.)  ? 

1 6.  Evaporate  5  cc.  of  pure  acetic  acid  (50  per  cent.) 
in  a  clean  porcelain  dish.     Is  there  any  residue? 

BASES 

The  most  common  and  useful  are  the  alkalies :  soda, 
potash,  ammonia  and  lime. 

Caustic  soda,  sodium  hydroxide  NaOH  is  a  deliques- 
cent white  solid  very  soluble  in  water  (212  parts  in  100 
cc.  cold)  and  develops  great  heat  during  solution. 


78  HOUSEHOLD    CHEMISTRY 

The  solid  as  well  as  solution  absorbs  CO2  from  the  air, 
forming  sodium  carbonate,  hence  should  be  kept  in  close- 
ly stoppered  bottles.  Caustic  soda  also  attacks  glass, 
especially  when  the  surface  is  roughened,  therefore,  it 
is  necessary  to  coat  glass  stoppers  or  stop-cocks  with 
heavy  hydrocarbon  when  used  in  contact  with  this 
liquid. 

Aqueous  solutions  of  10  and  20  per  cent.,  and  an  al- 
coholic solution  of  four  per  cent,  normal  solution,  are 
useful  in  the  laboratory.  Caustic  soda  solutions  are 
used  largely  in  neutralizing  acids  and  in  the  saponifica- 
tion  of  fats.  For  normal  solution  of  caustic  soda  see 
end  of  chapter. 

Caustic  potash,  potassium  hydroxide  KOH,  is  similar 
in  physical  and  chemical  'properties  to  caustic  soda, 
slightly  less  soluble  in  water  (200  parts  in  100  cc.  cold). 

Potash  being  the  weaker  and  more  expensive  alkali 
is  now  little  used  in  laboratory  and  commercial  opera- 
tions. 

Fats  saponified  with  potash  yield  very  soluble  and  del- 
iquescent products,  "soft  soaps"  in  contrast  to  the  drier 
sodium  compounds,  "hard  soaps." 

For  laboratory  purposes,  the  strength  of  aqueous  so- 
lutions is  the  same  as  for  soda. 

Ammonia,  ammonium  hydroxide,  aqua  ammonia,  a 
saturated  water  solution  of  the  gas  NH3  in  distilled  water 


ACIDS  AND  BASES    (ALKALIES)  79 

under  N.  T.  P.  conditions.  The  solution  has  a  sp.  gr. 
of  0.9  and  is  diluted  with  an  equal  volume  of  water  for 
general  use. 

Lime,  caustic  or  quicklime,  a  dry  white  solid,  is  pro- 
duced by  heating  carbonate  of  lime  in  the  form  of 
marble  or  limestone  to  a  white  heat  in  kilns,  the  opera- 
tion being  known  as  "lime  burning."  CaCO3=CaO-f- 
C02. 

Lime  has  a  strong  affinity  for  water  undergoing  the 
process  of  slaking,  during  which  considerable  heat  is 
evolved : 

CaO+H20=Ca(OH)2. 

If  the  water  is  absorbed  slowly  the  heat  is  given  off 
slowly  and  is  almost  imperceptible,  the  lime  masses  fall- 
ing as  a  soft  white  powder.  Lime  also  absorbs  CO2, 
reconstituting  CaCO3  from  which  it  was  derived  (air 
slaking). 

Slaked  lime  dissolves  sparingly  in  water  (i  part  in 
1200  cc.),  forming  a  clear  mildly  alkaline  liquid  known 
as  limewater.  A  supersaturated  solution,  milky  in  ap- 
pearance, is  known  as  milk  of  lime  (whitewash). 

Experiment  1. — Preparation  of  caustic  soda  or  potash, 
"causticing."  To  100  cc.  of  a  hot  20  per  cent,  solution 
of  Na2CO3  or  K2CO3,  add  milk  of  lime  in  small  por- 
tions until  a  small  filtered  sample  will  not  effervesce  with 
dilute  acid.  Boil  the  remainder  of  the  mixture  for  5- 


8O  HOUSEHOLD    CHEMISTRY 

10  minutes  and  allow  it  to  stand  until  the  white  precipi- 
tate has  completely  settled.  Draw  off  the  clear  liquid 
with  a  siphon  and  keep  in  a  well  stoppered  bottle;  when 
cold  determine  the  gravity  with  a  Beaume  hydrometer. 
A  16°  solution  is  the  strongest  that  can  be  made  by  this 
process;  stronger  solutions  are  obtained  by  evaporating 
the  liquid. 

Experiment  2. — Determine  the  sp.  gr.  of  various  so- 
lutions of  caustic  soda  and  potash. 

Experiment  3. — Neutralize  various  acid  solutions  with 
soda  of  potash. 

Experiment  4. — Boil  a  small  quantity  of  fat  or  oil  with 
an  equal  volume  of  16°  soda,  what  is  the  product? 

Experiment  5. — Dilute  strong  ammonia  with  one,  two 
and  four  volumes  of  water,  take  the  gravity  of  the  prod- 
ucts. Slowly  distill  the  weaker,  what  is  the  distillate, 
does  any  of  the  ammonia  remain  in  the  still? 

Experiment  6. — Prepare  lime  by  slaking  fresh  lump 
lime,  allowing  it  to  stand,  pouring  off  the  first  water 
containing  soluble  impurities.  Add  fresh  water  and  shake 
well.  The  second  clear  liquid  is  pure  limewater,  taste, 
expose  some  to  air  of  the  room  and  blow  the  expired 
breath  through  another  portion.  How  much  limewater 
does  it  take  to  neutralize  10  cc.  of  0.2  per  cent,  hydro- 
chloric acid,  to  neutralize  5  cc.  of  ordinary  vinegar,  and 
the  same  quantity  of  sour  milk  whey? 


ACIDS  AND  BASES    (ALKALIES)  8l 

NORMAL   SOLUTIONS   OF  ACID   AND    AT.KAT.T 

A  normal  solution  is  one  which  contains  the  hydro- 
gen equivalent  of  substance  in  grams,  in  one  liter  of 
solution.  For  all  monobasic  acids  and  alkalies  the  hy- 
drogen equivalent  corresponds  with  the  molecular  weight 
of  the  compounds;  for  dibasic  substances  it  is  one-half 
of  the  molecular  weight.  In  similar  manner  tri-  and  tet- 
rabasic  bodies  have  hydrogen  equivalents  corresponding 
to  one-third  and  one-quarter  of  their  molecular  weight. 

Normal  solutions  may  be  made  of  one-tenth  or  one- 
hundredth  of  their  full  strength,  either  by  taking  the 
corresponding  fractions  of  their  respective  equivalents 
or  by  diluting  the  full  normal  solutions  proportionately; 
they  are  known  as  deci-  and  centi-normal  solutions  re- 
spectively. 

To  explain  the  preparation  of  the  normal  solutions  of 
acid  and  alkali,  one  example  from  each  class  will  suffice 
and  as  hydrochloric  acid  and  caustic  soda  have  the  most 
extensive  application,  their  preparation  will  be  given. 
Neither  the  acid  nor  the  alkali  can  be  weighed  or  meas- 
ured with  accuracy,  hence  it  is  first  necessary  to  make  up 
solutions  of  some  acid  or  alkali  which  can  be  made 
exact.  Sodium  carbonate,  whose  equivalent  is  53,  can 
be  obtained  of  a  high  degree  of  purity  and  may  be 
weighed  exactly.  It  is  hardly  necessary  to  make  up  a 
large  quantity,  so  that  5.3  grams  of  pure  dry  soda  are 


82  HOUSEHOLD    CHEMISTRY 

usually  weighed  accurately,  dissolved  in  the  least  quan- 
tity of  water  and  the  resulting  solution  diluted  to  exactly 
loo  cc.  at  or  about  60°  F.  This  constitutes  the  exact 
normal  soda,  I  cc.  of  which  contains  5.3  milligrams  of 
soda. 

Of  the  hydrochloric  acid,  36.5  grams  are  needed  but  as 
it  is  a  volatile  liquid  and  cannot  be  weighed  with  any 
accuracy,  it  is  usual  to  calculate  the  volume  of  the  liquid 
from  its  specific  gravity  and  weight,  and  to  measure  out 
the  result  in  cubic  centimeters,  allowing  a  little  for  loss. 
The  calculation  is  simple  and  is  made  as  follows :  divide 
the  equivalent  in  grams  (36.5)  by  the  specific  gravity  of 
the  concentrated  acid  (1.2);  this  gives  30.4  -|-  as  a 
quotient  and  is  the  number  of  cubic  centimeters  to  be 
used  if  the  acid  were  pure,  but  the  strongest  acid  is  only 
40  per  cent.,  hence  this  quotient  must  be  multiplied  by 
2.5  (30.4  X  2.5  =  76  cc.).  It  is  safe  to  take  78-80 
cc.,  adding  it  to  300  or  400  cc.  of  distilled  water  and 
when  cool  diluting  to  exactly  one  liter.  To  fix  the 
strength  exactly  and  make  it  equivalent  to  the  soda 
solution  proceed  as  follows:  Measure  10  cc.  of  the 
soda  very  exactly  with  a  pipette,  run  it  into  a  small 
beaker  containing  about  100  cc.  of  distilled  water,  and 
add  two  or  three  drops  of  methyl  orange  solution.  Fill 
a  burette  with  the  acid  solution.  Note  the  level,  and  run 
it,  drop  by  drop,  with  constant  stirring,  into  the  soda. 
Stop  when  the  last  drop  changes  the  color  from  yellow 


ACIDS  AND  BASES    (ALKALIES)  83 

to  pink  which  remains  even  after  stirring  for  some 
moments.  Read  the  burette  and  note  the  number  of 
cubic  centimeters,  and  fractions  used.  Say  the  quantity 
is  9.8  cc.,  indicating  that  this  quantity  contains  as  much 
acid  as  should  exist  in  10  cc. ;  consequently,  980  cc.  of 
the  liquid  should  be  diluted  to  one  liter.  If  the  total 
amount  of  acid  is  less,  calculate  what  bulk  it  should 
occupy  and  dilute  accordingly.  The  acid  keeps  very 
well  but  should  be  preserved  in  tightly  stoppered  glass 
bottles  to  prevent  evaporation. 

The  caustic  soda  is  deliquescent  and  absorbs  carbon 
dioxide  so  must  be  weighed  rapidly  and  approximately, 
using  rather  more  than  the  40  grams  required,  say  50 
grams.  This  is  dissolved  in  300  or  400  cc.  of  water, 
cooled  and  diluted  to  one  liter.  Draw  off  10  cc.  of  the 
normal  acid  in  a  pipette,  allow  it  to  run  into  a  small 
beaker  containing  about  100  cc.  of  distilled  water,  and 
add  a  few  drops  of  phenolphthalein.  Fill  a  clean,  dry 
burette  with  the  caustic  soda.  Note  its  level  and  run 
it,  drop  by  drop,  with  constant  stirring,  into  the  acid 
solution  until  a  faint  but  distinct  pink  tint  remains  after 
stirring  for  some  moments.  Read  off  the  quantity  used, 
say  9.5  cc.,  showing  the  solution  to  be  too  strong  and 
requiring  dilution  as  in  the  case  of  the  acid.  After 
performing  this  operation  the  acid  and  the  alkali  should 
be  correct  and  I  cc.  of  one  will  exactly  neutralize  an 
equal  quantity  of  the  other. 


84  HOUSEHOLD    CHEMISTRY 

To  test  unknown  substances,  first  determine  the  body 
present  by  qualitative  analysis,  and  then  weigh  or  meas- 
ure some  convenient  quantity,  dissolve  or  dilute  with 
distilled  water,  add  the  indicator  and  run  in  the  acid 
or  the  alkali  until  the  neutral  point  is  reached.  Observe 
the  number  of  cubic  centimeters  used  and  multiply  each 
by  its  value  in  milligrams  of  the  substance  sought  and 
divide  the  result  by  the  quantity  used;  multiplying  this 
quotient  by  100  will  yield  per  cent. 

Value  of  i  cc.  of  normal  soda  in  each  of  the  following : 

Sodium  carbonate 0.053 

Acetic  acid 0.060 

Lactic  acid 0.090 

Tartaric  acid 0.075 

Citric  acid 0.064 

Hydrochloric  acid 0.0365 

Nitric  acid 0.063 

Sulphuric  acid 0.049 

Potassium  hydroxide 0.056 

Ammonium  hydroxide °-°35 

Calcium 0.037 


Chapter  VH 

GLASS,  POTTERY,  AND  PORCELAIN 

These  substances  belong  to  a  series  of  infusible  and 
insoluble  silicates  of  great  utility  in  all  household  opera- 
tions. Glass  consists  of  a  mixture  of  silicates  in  the 
amorphous  state  and  is  highly  prized  on  account  of  its 
brilliancy  and  transparency;  the  mass  may  be  colored 
without  affecting  either  of  these  qualities.  The  usual 
varieties  of  glass  consist  of  a  mixture  of  alkaline  (with 
alkaline  earth)  or  heavy  metal  silicates,  and  are  known 
as  Bohemian,  Crown,  Bottle  and  Flint  glasses. 

Bohemian  glass  is  a  silicate  of  potash  and  lime.  It  is 
very  infusible  and  insoluble,  therefore  especially  adapted 
for  chemical  purposes.  Two  varieties,  hard  and  soft, 
are  mentioned  in  the  introductory  chapter. 

Window  or  Crown  glass  is  a  silicate  of  soda  and  lime. 
It  is  more  fusible  but  harder  than  the  Bohemian  and  is 
more  easily  affected  by  acids. 

Bottle  glass  is  an  impure  variety  of  the  above,  colored 
with  iron. 

Flint  glass  is  a  potash  lead  silicate.  This  is  the  most 
fusible  kind  of  glass  and  is  easily  attacked  by  chemical 
reagents;  on  account  of  its  high  refractive  power,  it  is 
much  used  for  optical  purposes. 


86  HOUSEHOLD    CHEMISTRY 

All  kinds  of  glass  are  prepared  by  fusing  more  or  less 
pure  silica  in  the  form  of  sand  or  powdered  quartz  with 
the  potash  or  soda  and  lime  or  red  lead,  for  many  hours 
in  large  earthenware  pots,  heated  in  appropriate  fur- 
naces. When  the  mass  has  cleared,  it  is  cast  or  blown 
and  cooled  rapidly  in  order  to  retain  its  transparency. 

Annealing  is  a  process  of  heating  to  a  temperature 
short  of  softening  and  cooling  slowly,  thereby  reducing 
the  brittleness. 

While  transparency  is  a  very  important  property  of  all 
glasses,  there  are  several  useful  opaque  forms.  Opaque 
glass  is  the  result  of  suspending  finely  divided  infusible 
material  in  the  molten  mass.  Such  materials  are  bone 
phosphate,  cryolite,  zinc  or  tin  oxides,  etc.  The  enamels 
used  on  cooking  utensils  are  of  similar  composition. 

One  of  the  most  characteristic  properties  of  all  glasses 
is  the  solvent  effect  of  hydrofluoric  acid  and  soluble 
fluorides.  Etching  on  glass  is  largely  accomplished  by 
this  means. 

Colored  glass  is  the  result  of  dissolving  some  appro- 
priate mineral  oxide  in  either  variety  'of  glass : 

Ruby — oxide  of  gold  or  copper. 

Topaz — sulphide  of  antimony. 

Yellow — silver  chloride  or  borate. 

Green — oxide  of  chromium. 

Blue — oxide  of  cobalt. 

Amethyst — oxide  of  manganese. 


GLASS,  POTTERY,  AND  PORCELAIN          87 

EXPERIMENTS 

1.  Effect  of  Sudden  Cooling. — Heat  glass  tubing  strong- 
ly in  the  Bunsen  flame  until  it  softens  and  immediately 
plunge  into  water.     Note  the  effect.     This  change  will 
take  place  even  in  cold  dry  air  or  sudden  contact  with 
a  cold  surface. 

2.  Effect  of  Slow  Cooling. — Heat  as  before,  but  finally 
coat  with  carbon  by  cutting  off  the  air  supply  to  the 
burner.     When  cool  enough  to  handle,  wipe  off  the  car- 
bon with  clean  dry  filter-paper,  and  note  that  the  glass 
has   not  changed. 

3.  Corrosive  Action  of  Alkalies. — Half  fill  common  pre- 
scription bottles  (4  oz.)  with  strong  caustic  soda  solu- 
tion.    Place  them  in  warm  salt  water,  bring  slowly  to  a 
boil  and  continue  for  at  least  one  hour,  then  cool  slowly, 
pour  out  the  contents,  rinse  with  clean  water  and  ex- 
amine the  inner  surface. 

4.  Etching  Tests. —  (a)  With  a  clean  steel  pen  and  di- 
lute HF,  write  your  name   and   the  date   on   a   clean 
microscope   slide. 

(b)  Thinly  cover  a  clean  watch-glass  with  warm 
paraffin.  When  cool  cut  your  name  with  a  pencil  point 
through  the  paraffin  and  immediately  invert  over  a  lead 
dish  containing  a  mixture  of  fluorspar  and  concentrated 
sulphuric  acid.  After  half  an  hour's  standing,  rub  off 
the  paraffin  and  examine  the  result. 


88  HOUSEHOLD    CHEMISTRY 

5.  Detection  of  Arsenic,  Lead,  Etc. — Fuse  finely  ground 
chips  of  kitchen  utensil  enamel  with  an  excess  of  po- 
tassium sodium  carbonate  in  an  iron  or  nickel  crucible, 
cool  and  extract  the  melt  with  hot  water.  Filter,  and 
wash  the  residue  several  times  with  hot  water.  Test 
the  filtrate  for  arsenic,  lead,  and  acids  by  dividing  it 
into  three  parts — two  of  one-quarter  each  and  the  third 
the  remaining  half. 

Part  I.  Test  for  arsenic  by  making  strongly  acid 
with  HC1  and  boiling  with  a  strip  of  clean  copper.  A 
gray  or  black  coating  indicates  arsenic. 

Part  II.  Make  acid  with  HC1  and  pass  H2S  rap- 
idly through  the  solution.  A  black  precipitate  indicates 
lead. 

Part  III.  One-half  of  the  solution — tests  for  sulphates, 
borates,  phosphates,  and  silicates,  as  follows : 

Neutralize  with  HC1,  if  any  precipitate  forms,  filter 
and  divide  the  filtrate  into  three  parts.  The  residue  is 
silicates.  Take  one  part  of  the  filtrate,  thoroughly 
moisten  a  strip  of  turmeric  paper  with  it  and  dry  at  100° 
C.  A  pink  color  indicates  borates. 

To  another  part,  add  barium  chloride  and  a  few  drops 
of  HC1.  A  white  crystalline  precipitate  indicates  sul- 
phates. Pour  a  few  drops  of  the  remaining  part  into  an 
excess  of  ammonium  molybdate.  Warm  gently  and  a 
yellow  color  or  yellow  crystalline  precipitate  indicates 
phosphate. 


GLASS,  POTTERY,  AND  PORCELAIN          89 

Porcelain  and  Pottery  are  fused  silicates  of  alumina, 
the  former  pure,  and  the  latter  contaminated  with  oxides 
of  iron,  manganese,  etc. 

The  primary  source  of  these  wares  is  clay,  a  hydrated 
silicate  of  alumina,  highly  infusible.  For  porcelain  mak- 
ing it  is  mixed  with  some  fusible  silicate  such  as  feld- 
spar, and  a  small  quantity  of  water,  moulded  into  shape, 
dried  and  heated  in  a  furnace  for  many  hours.  The 
feldspar  or  flux  only  melts  and  running  through  the 
porous  mass  cements  it  together.  Even  after  firing,  the 
ware  requires  coating  with  the  glaze,  a  mixture  of  slight- 
ly fusible  material  suspended  in  water  into  which  the  ar- 
ticle is  dipped.  It  is  dried  and  returned  to  the  furnace 
for  heating.  The  glaze  is,  in  effect,  a  true  glass  and 
makes  the  mass  impenetrable  to  liquids.  Decorative 
effects  are  produced  in  two  ways ;  called  under-  and  over- 
glaze,  of  which  the  former  is  the  better  and  more  perman- 
ent. For  under-glaze  work,  finely  ground  colored  glass 
suspended  in  turpentine  is  applied  to  the  unglazed  ware 
and  aftenvards  "fired"  at  the  high  temperature  of  the 
porcelain  furnace.  The  glaze  is  subsequently  applied 
and  fired  as  before.  Over-glaze  decoration  admits  of  the 
use  of  colors  which  may  be  injured  by  the  high  heat  of 
the  porcelain  furnace  and  is  applied  at  a  lower  tempera- 
ture in  a  muffle.  The  colors  consist  o,f  various  oxides 
mixed  with  borax,  litharge,  nitre,  etc.  They  are  applied 
in  watery  solution. 


9O  HOUSEHOLD    CHEMISTRY 

Stoneware  is  an  impure  form  of  porcelain,  somewhat 
more  fusible  and  usually  glazed  with  borax.  The  finer 
qualities  are  known  as  china.  Earthenware  and  brick 
consist  of  clay  and  sand,  mixed  with  water,  moulded, 
dried  and  fired  in  a  kiln,  the  former  is  usually  glazed 
with  salt,  while  the  latter  is  left  in  the  porous  state. 

EXPERIMENTS 

1.  Compare  the  relative  translucency,   hardness,  and 
brittleness  of  porcelain,  china,  and  earthenware. 

2.  Testing  the  Glaze. — Boil  small  pieces  of  decorated 
china  in  caustic  soda  or  carbonate  of  soda  solutions  (10 
per  cent.)    for  some  time    (i   hour).     Cool,  wash  and 
compare  with  untreated  pieces. 

3.  Porosity. — Weigh  small  pieces  of  dry  unglazed  por- 
celain and  earthenware,  soak  over  night  in  water,  wipe 
dry  and  weigh  again.     Calculate  the  per  cent,  of  water 
absorbed. 

4.  Fusibility. — Heat  small  splinters  of  porcelain  and 
earthenware  held  in  platinum  wire  (spiral)  at  the  high- 
est heat  of  your  burner.     Cool  and  examine  with  a  mag- 
nifier.    Are  the  edges   sharp  or  rounded? 

5.  Testing  for  Lead  in  the  Glaze. — Boil  the  article  for 
some   time   in   caustic   soda,   cool   the    liquid   and   add 
(NH4)2S.     A  darkening  of  the  liquid  or  a  black  pre- 
cipitate indicates  lead. 


Chapter  VHI 

PAINTS  AND  VARNISHES 

These  substances  serve  primarily  as  a  protective  coat- 
ing, for  wood,  metal  and  masonry  surfaces ;  in  a  second- 
ary sense,  they  are  used  for  decorative  effect. 

Paint  consists  of  some  amorphous  solid  called  the 
base,  suspended  in  a  liquid  known  as  the  vehicle.  Any 
insoluble  coloring  matter  may  be  added  for  tinting  pur- 
poses. Two  kinds  of  paint  are  commonly  used;  viz., 
water,  and  oil.  The  simplest  water  paint  is  whitewash 
or  milk  of  lime,  with  or  without  salt  or  plaster  to  in- 
crease the  adhesive  quality.  Whitewash  losses  water 
(dries)  and  absorbs  CO2,  turning  to  chalk,  CaCO3. 
Kalsomine  is  finely  ground  chalk  suspended  in  a  warm 
dilute  solution  of  glue.  It  is  applied  warm  and  dries 
and  hardens  on  cooling.  Any  appropriate  coloring  mat- 
ter may  be  mixed  with  either  of  the  above.  Since  these 
mixtures  are  largely  compounded  of  water,  they  will  not 
be  permanent  when  exposed  to  moisture  or  dampness; 
hence  their  use  is  confined  to  the  interior  of  buildings. 
Mixtures  of  boiled  soap  and  lime  or  skimmed  milk  and 
lime,  usually  classed  as  whitewashes,  become  so  insoluble 
on  exposure  to  air,  that  they  are  superior  in  lasting  quali- 
ty to  any  except  the  best  oil  paints. 

Oil  paints  contain  as  base,  either  white  lead    (basic 

7 


92  HOUSEHOLD    CHEMISTRY 

carbonate  of  lead,  Pb(OH)2,  PbCO3)  or  zinc  white 
(ZnO)  or  a  mixture  of  both,  suspended  in  the  vehicle, 
linseed  or  poppy  seed  oils.  When  mixed,  the  base  and 
oil  form  soaps,  soluble  in  the  excess  of  oil  present,  but 
not  in  water.  During  the  drying  operation,  the  oil  ab- 
sorbs oxygen  and  solidifies  to  a  tough  elastic  body.  This 
latter  action  is  however  quite  slow,  hence  driers  (com- 
pounds of  manganese)  are  used  to  hasten  the  absorption 
of  atmospheric  oxygen.  Spirits  of  turpentine  (C10H16) 
commonly  called  "Turps"  are  useful  in  thinning  the  paint 
mass  and  causing  it  to  penetrate  the  freshly  painted  sur- 
face. Turps  also  dulls  or  flats  the  otherwise  glistening 
surface  of  the  dried  paint,  but  renders  it  at  the  same 
time  noticeably  susceptible  to  the  action  of  moisture. 
As  in  the  case  of  water  paints,  mineral  colors  ground 
in  oil  are  used  for  tinting.  The  following  is  a  list  of 
the  most  lasting: 

Reds — Indian,  Venetian,  Tuscan   (oxides  of  iron). 
Yellows — Ochre  (oxide  of  iron),  Chrome  (chromate 
of  lead). 

Brown — Umber  (manganese  clay)  Sienna. 
Blue — Prussian  Blue. 

Green — Prussian  Blue  and  Chrome  Yellow. 
Black — Lamp-  or  Bone-black  (carbon). 

Oil  paints  are  best  applied  in  at  least  three  successive 
coats.  First  or  priming  coat  is  pure  white  lead  and  oil 
with  abundance  of  turps.  This  coat  sinks  in  and  dries 


PAINTS    AND    VARNISHES  93 

rapidly.  Second  or  body  coat  is  pure  zinc  and  lead 
base,  linseed  oil  and  drier.  It  is  much  thicker  than  the 
previous  coat  and  takes  longer  to  harden  and  dry.  Fin- 
ish coat  is  much  like  the  body  coat  but  thinner;  in  rare 
cases  it  may  contain  a  little  turps  for  flattening  effect. 

Varnishes  are  of  two  kinds — spirit  and  oil. 

Spirit  varnishes  consist  of  gum  resins  dissolved  in 
alcohols;  for  instance,  shellac  and  the  less  common 
lacquers.  As  the  solvent  evaporates,  the  gum  remains 
as  a  continuous  coat.  Because  of  their  light  color  and 
transparency,  they  are  much  used  in  covering  wood-work. 
Shellac  is  tender  and  spots  with  water;  hence  its  use  is 
limited  to  furniture,  metals  and  interior  wood-work. 

Oil  varnishes  are  prepared  by  dissolving  fossil  resins 
in  hot  linseed  oil,  an  operation  requiring  much  skill  and 
time.  After  aging  for  several  months  they  are  ready 
for  use.  Many  varieties  receive  an  addition  of  turps 
before  use,  especially  if  used  for  interior  work.  A  good 
oil  varnish  will  outlast  even  the  best  paint  and  if  ap- 
plied as  a  finishing  coat  will  increase  its  life  many 
times.  Carriages,  railway  coaches  and  automobiles  are 
painted  in  this  manner. 

It  is  a  good  plan  never  to  dilute  any  varnish  of  stand- 
ard make  if  you  expect  the  best  results. 

EXPERIMENTS 
1.  Testing  Water  Paints. — Evaporate  a  small  portion 


94  HOUSEHOLD    CHEMISTRY 

in  a  porcelain  dish.  As  the  mass  dries,  observe  the  odor. 
Does  it  suggest  glue?  Does  the  residue  blacken,  indicat- 
ing organic  matter?  Ignite  until  white  or  nearly  so, 
cool  and  add  dilute  acetic  acid.  Any  effervescence  is 
probably  due  to  CO,,  indicating  carbonates.  Is  the  mass 
entirely  soluble  in  acetic  acid ;  if  not  pour  off  the  liquid, 
test  it  for  lime  and  add  dilute  HC1  to  the  residue.  Heat 
this  for  same  time,  finally  driving  off  the  acid,  cool  and 
add  water.  Is  the  residue  gritty,  indicating  silica,  SiO2  ? 

2.  Testing  Oil  Paints — Preferably  White. — Half  fill  a 
clean  4  oz.  vial  with  gasoline,  add  about  one  teaspoonful 
of  the  sample,  cork  and  shake  well.     Lay  it  aside  to  set- 
tle, then  pour  off  the  clear  liquid,  add  more  gasoline  to 
the  vial  and  shake  again.     Repeat  this  once  more,  finally 
pouring  the  whole  contents  into  a  shallow  dish  or  saucer 
and   drive   off   the    remaining   solvent   over  hot   water. 
Carefully  evaporate  a  portion  of  the  gasoline  filtrates 
and  observe  the  thick  oily  residue.     Add  to  it  two  drops 
of  HaSO^  cone.;  does  it  form  brown  rings  where  the 
acid  drops  fall   (indication  of  linseed  oil)?     The  dried 
residue,   freed  from  gasoline,  should  dissolve  in  dilute 
acetic  acid  (freedom  from  clay,  barites,  etc.).     Pass  H2S 
through  the  solution  and  filter  off  the  black  precipitate 
of  PbS.     To  the  filtrate  add  NH4OH  cautiously ;  a  white 
precipitate  indicates  Zn. 

3.  Testing  Varnishes. — Little  or  nothing  can  be  done  in 


PAINTS    AND    VARNISHES  95 

a  simple  way  to  identify  the  gums,  but  some  indication 
of  the  solvent  may  be  obtained  by  the  following  method : 
Distill  a  small  quantity  of  the  varnish  and  examine 
the  distillate  for  alcohol,  turpentine  and  benzine.  The 
odor  is  usually  sufficient  indication;  also  not  the  tem- 
perature of  distillation. 


Part  II 

Chapter  IX 

Food  Principles. — There  are  types  of  chemical  com- 
pounds that  serve  to  maintain  heat,  muscular  energy 
and  repair  work  of  organisms.  Carbohydrates,  fats, 
proteins  and  mineral  salts  are  the  accepted  forms. 

Carbohydrates. — A  series  of  compounds  of  the  alcohol 
and  aldehyde  type,  containing  C,  H  and  O.  The  H  and 
O  atoms  in  the  ratio  of  2:1  and  the  C,  six  or  some 
multiple.  Familiar  examples  of  these  compounds  are 
starch,  cellulose,  sugar,  glucose,  etc. 

The  carbohydrates  are  divided  into  three  groups: 

1.  Monosaccharids — glucoses,   CGH12O6. 

2.  Disaccharids — sugars,  C^H^O^. 

3.  Polysaccharids — celluloses  and  starches  wC6H10O5. 

Both  poly-  and  disaccharids  are  convertible  into  mono- 
saccharids  by  the  process  of  hydrolysis,  which  consists 
in  the  absorption  of  H  and  O  as  they  exist  in  water ;  this 
process  may  be  carried  out  in  a  variety  of  ways,  two  of 
which  acid  and  enzyme  hydrolysis  are  most  important. 

Ultimate  Composition. — i.  Determination  of  Hydrogen 
and  Oxygen  Evolved  as  Water. — Heat  about  I  gram  of 


FOOD  PRINCIPLES  97 

granulated  sugar  in  a  clean  dry  test-tube.    Observe  the 
condensation  of  moisture  in  the  cooler  part  of  the  tube. 

2.  Determination  of  Carbon,  (a)  By  direct  heat  con- 
tinue heating  and  note  the  blackening  of  the  mass  due 
to  freeing  of  some  of  the  carbon.  (&)  By  dehydration. 
Treat  about  I  gram  of  the  sugar  in  a  porcelain  evaporat- 
ing dish  with  a  little  concentrated  sulphuric  acid,  heat 
gently  and  note  the  blackening  effect.  In  this  case,  the 
concentrated  sulphuric  acid  withdraws  the  hydrogen  and 
oxygen  in  the  form  of  water  and  leaves  the  carbon. 

?.  Determination  of  Hydrogen  and  Carbon  in  the  Form 
of  Hydrocarbons,  i.e.  Tarry  Bodies. — Observe  the  pun- 
gent odor  of  the  vapors  arising  from  the  tube  during 
the  heating  in  experiment  2,  (a).  This  usually  condenses 
on  the  cooler  part  of  the  tube  in  the  form  of  a  dark 
brown  liquid  (caramel). 

STARCH  (C6H)005), 

Starch,  a  complex  plant  product  is  formed  in  the  leaf 
from  atmospheric  moisture  and  carbon  dioxide,  through 
the  agency  of  sunlight  and  chlorophyl  according  to  the 
following : 

H2O+CO2:=HCHO+O2  by  condensation.  6HCHO= 
C6H1206.  By  dehydration,  C6H12O6rr:C6H10O5+H2O. 


98  HOUSEHOLD    CHEMISTRY 

The  formula,  CGH10O5,  does  not  express  the  ultimate 
composition  of  starch,  but  merely  the  ratio  in  which 
the  constituents  always  occur.  The  actual  formula  is 
some  large  multiple  of  this  simple  form,  which  serves 
however  for  all  practical  purposes. 

Starch  thus  formed  is  stored  up  by  the  plant  in  min- 
ute particles  known  as  granules,  varying  in  size  and 
shape.  The  larger  and  simpler  forms  are  found  in 
the  roots,  the  smaller  in  the  seeds.  There  is  no  known 
chemical  difference  in  these  various  forms. 

In  general  terms  raw  starch  consists  of  a  mass  of 
unbroken,  and  cooked  starch  of  broken  granules. 

Raw  starch  is  a  white  opaque  solid,  neutral  in  reaction, 
insoluble  in  cold  water,  alcohol  and  ether.  Heated  to 
250°  F.  it  begins  to  decompose  darkening  in  color,  giv- 
ing off  an  odor  of  burning  wood  and  acid  vapor;  at 
higher  temperatures,  it  chars  and  leaves  a  porous  mass 
of  carbon.  If  starch  is  held  in  suspension  in  water  and 
gradually  heated  at  160°  F.,  it  begins  to  gelatinize  due 
to  bursting  of  the  granules ;  at  or  about  212°  this  change 
takes  place  rapidly. 

A  solution  of  iodide  in  potassium  iodide  and  water, 
colors  raw  or  cooked  starch  blue,  provided  the  mass  is 
cool  and  either  neutral  or  acid:  the  reaction  is  due  to 
the  formation  of  iodide  of  starch  of  indefinite  composi- 
tion. Gelatinized  starch  is  slightly  soluble  in  cold  water. 


FOOD  PRINCIPLES  99 

By  hydrolysis  starch  changes  slowly  into  dextrines, 
maltose  and  glucose  (dextrose)  as  follows: 

2C0H1005+H20=C12H22011. 

C12H22011+H20=2C6H1206. 

Two  per  cent,  of  mineral  acid  H2SO4  or  HC1  is  the 
amount  usually  employed,  slight  pressure  during  boil- 
ing greatly  shortens  the  operation. 

One-tenth  of  one  per  cent,  or  less  of  enzyme  (diastase) 
at  150-160°  F.  rapidly  converts  starch  into  dextrine  and 
maltose,  but  the  final  stage  must  be  completed  by  acid. 

Starch  is  rapidly  soluble  in  concentrated  sulphuric 
acid  (hydrolysis).  It  unites  with  concentrated  nitric 
acid  in  varying  proportions,  forming  nitrates,  very  un- 
stable compounds  (explosives). 

In  presence  of  cold  strong  fixed  alkali,  starch  is  solu- 
ble with  partial  hydrolysis  and  usually  the  product  has 
a  distinct  yellow  color;  weaker  solutions  have  very  little 
effect  unless  heated. 

EXPERIMENTS 


ORDINARY  STARCH  DERIVED  FROM  POTATOES  OR  CORN 

1.  Occurrence  of  Starch. — Examine  a  thin  section  of 
potato  under  the  microscope.  Make  a  careful  drawing 
of  the  structure  of  the  cells  and  the  granules  within. 
Cover  the  section  with  a  thin  glass  and  introduce  a 
minute  trace  of  iodine  solution  at  the  edge  of  the  cover 


TOO  HOUSEHOLD    CHEMISTRY 

glass.     Note  and  make  a  colored  (blue  pencil)  diagram 
of  the  result. 

2.  Extraction  of  Starch. — Clean  and  peel  one  end  of  a 
small  potato,  rub  it  on  an  ordinary  grater,  collect  the 
gratings  in  a  beaker  of  cold   water,   strain,   allow  the 
cloudy   liquid   to   stand   until   starch   settles.      Pour   off 
liquid  and  use  the  sediment  for  following  tests: 

3.  Effect  of  Dry  Heat.— Gently  heat  half  an  inch  of 
dry  starch  in  a  clean,  dry  test-tube  observe  and  explain 
condensed  moisture  in  the  cooler  part  of  the  tube.     In- 
crease the  heat   somewhat   and  note   the  odor   of   the 
evolved  vapor  and  the  color  of  the  starch:  what  does 
it  suggest  ?    Now  heat  strongly  until  only  a  black  residue 
remains :  what  is  it  ? 

4.  Effect  of  Strong  Acid. — To  a  small  portion  of  dry 
starch  in  porcelain  evaporating  dish  add  a  few   drops 
of  concentrated  sulphuric  acid;  note  the  result  and  after 
a  short  time  heat  gently  and  observe  again. 

5.  Solubility. — Treat  a  small  portion  of  finely  pulver- 
ized  dry   starch  with  cold  water,   filter  a  portion  and 
examine  the  filtrate  fo/  dissolved  material,  by  evaporating 
a  little  on  platinum  foil :  also  by  the  iodine  test. 

6.  Soluble  Starch. — Boil  the  remainder  of  the  starch 
and  water  mixture;  it  gelatinizes.     Filter  some  of  this 
and  test  the  clear,  cold  filtrate  with  iodine.     Explain. 
To  the  remainder  when  cool  add  a  minute  portion  of 


FOOD  PRINCIPLES  IOI 

iodine  solution:  it  is  colored  blue.  Gently  heat  this  and 
allow  to  cool  again :  note  the  result.  Now  boil  for  some 
time,  cool,  the  color  will  not  return.  Examine  under 
the  microscope  portions  of  raw  and  cooked  starch,  with 
and  without  iodine. 

7.  Effect  of  Alkali. — To  some  starch  solution  in  a  test- 
tube  add  a  small  portion  of  caustic  soda  (NaOH)  and  a 
few  drops  of  iodine  solution  and  note  the  result.     Repeat 
the  experiment   using  dilute  sulphuric  acid  instead  of 
NaOH. 

8.  Effect  of  Tannic  Acid. — Add  a  solution  of  tannic 
acid  to  some  starch  solution.     Note  the  result,  also  any 
change  effected  by  heating. 

9.  Starch,  a  Colloidal  Substance. — Prepare  a  dialyzer  as 
directed  and  partly  fill  it  with  starch  solution,  then  stand 
the  whole  in  a  beaker  of  cold  water.    After  standing  for 
some  time  test  the  water  for  starch  with  iodine  solution. 

10.  Hydrolysis. — Make  a  very  weak  solution  of  starch 
in  about  four  ounces  of  boiling  water:  to  this  solution 
add  2  cc.  of  strong  hydrochloric  acid  and  boil  until  clear, 
using  a  reflux  condenser.     At  this  point,  a  small  quantity 
of  the  cooled  liquid  should  give  no  blue  coloration  with 
iodine  solution.     If  this  is  not  the  case  add  10  drops  of 
the  same  acid  and  boil  some  minutes  longer,  or  until  a 
small  portion  gives  no  test  with  iodine  as  above.     Now 
neutralize  the  remainder  of  the  liquid  with  sodium  car- 
bonate solution. 


IO2  HOUSEHOLD    CHEMISTRY 

11.  Pehling's  Test.— Prepare  Fehling's  solution  by  mix- 
ing 5  cc.  of  copper  sulphate  and  alkaline  Rochelle  salt 
(the  same  amount)   with  20  cc.  of  distilled  water,  boil 
the  solution  exactly  two  minutes.     During  this  period 
no  change  should  take  place  in  the  liquid.     Add  i  or  2 
cc.  of  the  neutralized  starch  solution  and  boil  again  for 
two  minutes.     Note  the  change  in  color  of  the  liquid 
and  when   cool,   the   red  precipitate  of   cuprous  oxide, 
Cu2O,  indicating  the  presence  of  a  reducing  sugar,  i.e. 
glucose.    If  the  indicated  changes  do  not  take  place  add 
more  solution  and  boil  again. 

12.  Enzyme  Hydrolysis. — Unorganized  ferments:  ptya- 
lin  from  saliva  or  diastase  from  malt.     Prepare  saliva 
in  the  following  way:  rinse  out  the  mouth  with  water, 
curve  the  tongue  so  as  to  place  its  tip  behind  the  upper 
incisor  teeth,  then   inhale  the  vapor  of  ether   or  even 
cold  air :  collect  the  saliva  in  a  small  test-tube,  dilute  with 
five  times  its  volume  of  water  and  filter  through  a  filter 
paper  perforated  with  a  pqint  of  a  pin.     The  filtered 
liquid  should  react  neutral  or  alkaline. 

Make  a  starch  solution  in  hot  water,  cool,  add  a  few  cc. 
of  saliva,  warm  (not  above  40°  C.)  until  clear,  cool  and 
test  with  (a)  iodine  solution,  and  (b)  Fehling's  solu- 
tion (maltose). 

To  a  weak  starch  solution  add  about  5  cc.  of  diastase 
solution  and  heat  to  65°  C.  As  soon  as  the  paste  be- 
comes clear,  test  a  portion  with  iodine  solution  and  con- 


FOOD  PRINCIPLES  IO3 

tinue  testing  other  portions  until  the  test  fails  to  give 
a  color  (maltose).  At  this  stage  boil  the  remainder  of 
the  solution  with  about  25  drops  of  dilute  sulphuric  acid 
for  ten  minutes.  Neutralize  and  test  this  with  Fehling's 
solution  (glucose). 

C  Erythrodextrine 
DEXTRINE     -I   Achrodextrine,  (C.H,,©,), 

[_  Maltodextrin 

Preparation. — Dextrine  or  "British  Gum"  is  prepared 
commercially  by  heating  starch  moistened  with  nitric 
acid.  It  may  be  prepared  more  conveniently  by  heating 
a  strong  starch  paste  with  moderately  dilute  sulphuric 
acid  until  clear,  cooling  and  precipitating  the  dextrine  by 
adding  to  ethyl  alcohol. 

Solubility. — Compare  the  solubility  of  dextrine  in  cold 
water  and  in  boiling  water. 

To  successive  portions  of  cooled  dextrine  solution  in 
test-tubes  add: 

1.  Iodine  solution. 

2.  Alcohol  up  to  60  per  cent,  by  volume. 

3.  Caustic  potash  and  iodine  solutions. 

4.  Sulphuric  acid  and  iodine  solutions. 

5.  A  few  drops  of  ammonia  and  basic  acetate  of  lead ; 
note  the  result. 

6.  To  boiling  Fehling's  solution:  if  pure  there  will  be 
no  reaction. 


104  HOUSEHOLD    CHEMISTRY 

7.  Tannic  acid  as  under  starch. 

8.  Take  about  25  cc.  of  clear  dilute  starch  solution 
in  a  small  beaker  and  add  2  or  3  cc.  of  undiluted  saliva, 
keep  at  body  temperature  and  from  time  to  time  pour 
off  small  portions  and  test  with  iodine  solution,  keeping 
each  for  comparison.     Note  the  gradual   change  from 
blue  to  red  to  yellow  and  finally  to  colorless.    The  stages 
are :  starch,  blue :  erythrodextrine,  violet :  achrodextrine, 
yellow:  maltodextrine,  colorless. 

GLYCOGEN  (CJ^flJx 

Preparation. — Grind  a  mixture  of  scallops  and  sand  in 
a  mortar,  transfer  to  a  beaker,  add  enough  water  to 
cover  the  mass  and  boil.  This  dissolves  the  glycogen 
and  partially  precipitates  the  proteins,  which  are  now 
completely  precipitated  by  partially  cooling  and  adding 
a  few  drops  of  acetic  acid.  Filter  and  add  the  filtrate  to 
alcohol  (95  per  cent.).  Glycogen  will  come  down  as  a 
white  precipitate.  Allow  to  settle,  decant  off  the  clear 
liquid,  and  filter  the  residue. 

Apply  the  following  tests  to  the  glycogen  thus  ob- 
tained : 

1.  Solubility  in  water;  look  for  opalescence. 

2.  Solubility  in  10  per  cent,  sodium  chloride  solution. 

3.  Solubility  in  hydrochloric  acid. 

4.  Solubility  in  caustic  potash. 

5.  Reaction  with  iodine  solution. 


FOOD  PRINCIPLES  105 

6.  Boil  in  a  beaker  for  fifteen  minutes  with  2  cc.  of  di- 
lute hydrochloric  acid,  neutralize  with  sodium  carbonate 
and  test  with  Fehling's  solution.  What  change  has  taken 
place  ? 

Glycogen  is  soluble  in  alcohol  from  0-60  per  cent,  and 
insoluble  in  alcohol  from  60-100  per  cent. 

CELLULOSES  (C6H1005)w 

These  compounds  represented  by  the  general  formula 
wC6H10O5  are  at  once  the  most  complicated  and  stable 
of  the  carbohydrates. 

They  may  be  roughly  divided  into  the  simple  and 
compound  celluloses,  the  former  unicellular  in  structure 
and  the  latter  multicellular. 

Cotton,  thistledown,  and  the  internal  fibrous  network 
of  grains  and  vegetables  are  simple  celluloses  and  occur 
as  ribbon-like  bands  with  curled  edges  and  a  characteristic 
corkscrew  twist.  These  forms  contain  little  protein,  gum, 
fat  or  mineral  matter.  Flax,  grasses  and  woody  fiber  are 
compound  celluloses,  occurring  for  the  most  part  as 
jointed  rods  or  tubes,  and  are  highly  charged  with  pro- 
tein, fat,  gum  and  mineral  matter.  Cotton  is  the  only 
unicellular  form  of  carbohydrate  of  industrial  import- 
ance, while  the  multicellular  type  has  many  representa- 
tives, i.e.,  linen,  hemp,  jute,  ramie  and  a  great  variety 
of  woods. 

The  treatment  of  cotton  does  not  involve  any  exten- 


IO6  HOUSEHOLD    CHEMISTRY 

sive  chemical  operations,  but  is  chiefly  confined  to 
mechanical  manipulation.  The  compound  celluloses  on 
the  other  hand  require  complex  and  prolonged  chemical 
or  bacterial  treatment  before  the  fiber  is  ready  for  the 
operations  of  spinning,  weaving  and  dyeing.  Woody 
fiber  is  now  generally  used  for  the  preparation  of  the 
felted  fabric  known  as  paper.  It  is  necessary  in  this  case 
to  remove  all  impurities  by  chemical  means,  and  to  break 
up  the  long  fibers  by  grinding  before  the  fabric  can  be 
prepared. 

General  Properties  of  the  Celluloses. — Celluloses  are  in- 
soluble in  water  hot  or  cold,  and  in  weak  acids  or  alkalies. 
Strong  acids  and  alkalies  cause  them  to  hydrolyze ;  in 
some  cases  soluble  forms  result  by  heating  or  prolonged 
action  in  the  cold,  or  by  a  combination  of  both  meth- 
ods. Generally  speaking,  the  action  of  acids  is  more 
rapid.  When  partially  hydrolyzed  they  are  colored  blue 
in  the  presence  of  iodine.  Nitric  acid  in  concentrated 
form  converts  cellulose  into  nitro  compounds  of  varying 
composition,  containing  one  to  six  nitro  groups ;  the  form 
depending  on  the  duration  of  the  nitrating  process.  All 
of  these  compounds  are  very  unstable  and  dissociate  into 
water,  carbon  dioxide  and  nitrogen,  when  slightly  heated ; 
hence  their  use  as  explosives.  Nitro  celluloses,  unlike 
cellulose,  dissolve  in  ether,  alcohol  or  acetone  or  mixtures 
of  these  solvents  (collodion)  and  on  evaporation  yield 
transparent  structureless  films ;  used  in  medicine,  photog- 


FOOD  PRINCIPLES  IO7 

raphy  and  for  the  preparation  of  artificial  silk.  Am- 
moniacal  cupric  oxide  (Schweitzer's  Reagent)  and  con- 
centrated zinc  chloride  dissolve  simple  cellulose  on  gentle 
warming.  Hydrocellulose  precipitates  from  these  solu- 
tions on  acidifying  with  acetic  acid. 

Lignocellulose  (wood)  yields  oxalic  acid  on  treatment 
with  nitric  acid,  and  oxalate  of  potash  on  fusion  with 
caustic  potash. 

Cellulose  fibers  of  both  types  do  not  readily  unite  with 
dyes,  but  require  previous  chemical  treatment  (mor- 
danting) to  develop  the  color  and  make  it  permanent. 

Cellulose  fibers  are  characterized  by  high  capillary 
capacity  and  heat  conductivity ;  hence  their  use  for  lamp 
wicks,  toweling  and  summer  clothing.  These  properties, 
however,  may  be  much  modified  by  high  twisting  and 
close  weaving,  as  in  the  case  of  canvas. 

GENERAL  TESTS 

(a)  Effect   of   Heat    (Charring). — Heat    a   piece   of 
fibrous  material  in  a  clean  dry  test-tube.     Note  the  odor 
of  the  gases  evolved  and  test  the  vapor  with  blue  litmus 
paper.    Examine  the  charred  mass  with  a  magnifier. 

(b)  Solubility  in  Water. — Try  to  dissolve  some  fi- 
brous material   in   water. 

(c)  Solubility  in  Concentrated  Sulphuric  Acid. — Add 
concentrated   sulphuric   acid   to    some   fiber.      Note   the 
effect. 

8 


IO8  HOUSEHOLD    CHEMISTRY 

(d)  Structure. — Examine  carefully  the  structure  of 
the  fibers  under  a  microscope. 

(?)  Crude  Fiber. — Crude  cellulose  of  wood,  grains, 
etc.,  is  determined  as  follows : 

Take  one  gram  of  the  dried,  ground  sample,  boil 
with  loo  cc.  of  il/4  per  cent,  sulphuric  acid,  when  cool 
strain  through  muslin.  Wash  once  with  hot  water. 
Scrape  the  residue  from  the  muslin  and  boil  it  with  100 
cc.  of  1%  Per  cent,  caustic  soda.  Strain  again  through 
the  same  piece  of  muslin,  wash  with  hot  water,  then 
with  alcohol,  and  finally  with  ether.  Weigh  the  dried 
residue. 

(/)  Method  for  Determining  the  Character  of  Fibers. 
If  a  mixed  cotton-linen  fabric  be  dipped  for  about 
one  minute  in  cold  concentrated  H2SO4  quickly  removed 
and  washed,  the  cotton  fibers  alone  will  be  dissolved. 

TESTS  ON  COTTON 

(a)  Structure. — Note  the  ribbon-like  structure  of  pure 
cotton  fiber. 

(b)  Breaking  and  Burning  Tests. — Unraveled  threads 
of  cotton  fabric  are  untwisted  and  broken  by  holding 
between  the  thumbs  and  index  fingers  and  pulled  apart 


FOOD  PRINCIPLES  lOQ 

slowly  and  steadily.  Cotton  breaks  suddenly  with  tas- 
selled  ends.  Burn  a  small  tuft  of  cotton  and  note  the 
condition  of  the  fiber  ends. 

(c)  Nitrating. — Treat  a  piece  of  filter-paper  (cotton) 
with  concentrated  nitric  and  sulphuric  acids,  keeping  the 
mixture  cool.    Several  nitrates  of  cellulose  may  form. 
The  hexa-  and  penta-nitrates  are  the  most  prominent. 
The  hexa-nitrate  of  cellulose  is  called  gun  cotton.    Wash 
the  product  in  water  and  dry.     Test  its  inflammability 
and  its  solubility  in  a  mixture  of  equal  parts  of  alcohol 
and  ether. 

(d )  Mercerization. — Soak  some  cotton  cloth  in  10  per 
cent,   caustic  soda  and   note  that   it  becomes   partially 
transparent — mercerized.      If    the    cloth    is    thoroughly 
washed  free  from  alkali  and  tested  with  iodine  solution, 
a  blue  color  appears. 

(e)  Solubility  in  Zinc  Chloride. — Dissolve  some  ab- 
sorbent cotton  in  acid  zinc  chloride  solution,  (ZnCl2  dis- 
solved in  twice  its  weight  of  cone.   HC1).     Precipitate 
by  dilution  and  compare  the   result   with  the  original 
substance. 

(/)  Solubility  in  Schweitzer's  Reagent. — Dissolve 
some  absorbent  cotton  in  Schweitzer's  reagent,  add  the 
resulting  solution  to  95  per  cent,  alcohol  and  compare 
the  precipitate  with  the  original  substance. 


IIO  HOUSEHOLD    CHEMISTRY 

TESTS  ON  LINEN 

(a)  Structure. — Examine  carefully  the  structure  of 
single  linen  fibers. 

(&)  Breaking  and  Burning  Tests. — Unraveled  threads 
of  linen  fabric  are  untwisted  and  broken  by  holding  be- 
tween the  thumbs  and  index  fingers  and  pulled  apart 
slowly  and  steadily.  Linen  parts  slowly,  and  with  point- 
ed ends. 

Burn  a  piece  of  linen  fabric  and  note  the  condition  of 
the  fiber  ends. 

(c)  Solubility  in  Concentrated  Sulphuric  Acid. — Treat 
a  piece  of  linen  cloth  with  concentrated  sulphuric  acid 
and  compare  with  the  effect  on  cotton  cloth. 

TESTS  ON  IIGNOCELLULOSE 

(a)  Structure. — Examine  carefully  the  character  of 
the  fibers. 

(b)  Phloroglucinol    Test.— Phloroglucinol,    in    HC1, 
gives  a  deep  magenta  coloration  with  any  of  the  ligno- 
celluloses. 

The  reagent  is  prepared  by  dissolving  the  phenol  to 
saturation  in  HC1  (1.06  sp.  gr.). 

(c)  Saturate  moist  jute  fiber,  held  in  a  glass  tube, 
with  chlorine  gas  and  then  pass  SO2  through  it.     Note 
the  characteristic  reaction  a  deep  magenta  color. 

TESTS  ON  PAPER 

Determine  starch  as  filler  with  iodine  solution.     De- 


FOOD  PRINCIPLES  III 

termine  "size"  with  Millon's  reagent.  If  protein  material 
is  present  a  white  precipitate,  turning  red  on  heating 
forms. 

Parchment  Test. — Dip  starch-free  paper  in  a  cold  mix- 
ture of  water  and  sulphuric  acid  (2 13),  withdraw  quickly, 
wash  in  clear  water  and  dry.  Compare  with  an  un- 
treated sample.  Does  it  respond  to  the  iodine  test, 
why? 

GLUCOSES  (C0H1206) 

These  bodies  are  now  regarded  as  aldehydes  of  the 
type  CH2OH(CHOH)4COH.  The  most  common  rep- 
resentatives are  known  as  glucose  or  grape  sugar,  fruc- 
tose or  fruit  sugar  and  galactose.  A  mixture  of  equal 
parts,  by  weight,  of  glucose  and  fructose  is  commonly 
called  invert  sugar.  The  essential  difference  in  these 
compounds  is  due  to  the  effect  and  degree  of  their  action 
on  polarized  light.  Glucose  causes  a  right  hand  devia- 
tion, fructose  a  left  hand,  galactose  a  right  hand;  but 
each  in  turn  varies  in  degree,  fructose  being  greater  than 
either  glucose  or  galactose. 

Glucoses  are  very  soluble  in  water  and  more  soluble 
in  alcohol  than  other  carbohydrates.  As  aldehydes  they 
reduce  alkaline  solutions  of  metallic  salts,  to  the  metallic 
state  or  some  low  form  of  oxide  (see  silver  mirror  test 
page  66  and  Fehling's  reaction,  page  102).  All,  however, 


112  HOUSEHOLD    CHEMISTRY 

in  the  same  quantitative  proportions.     The  osazones  are 
formed  by  the  phenylhydrazine  reaction. 

Glucoses  are  formed  during  the  acid  hydrolysis  of  other 
carbohydrates  as  follows:  Cellulose,  starch  and  maltose 
yield  glucose  exclusively;  lactose  yields  a  mixture  of 
glucose  and  galactose ;  sucrose  yields  a  mixture  of  glu- 
cose and  fructose.  Since  sucrose  is  dextro-rotatory  and 
on  hydrolysis  yields  a  mixture  of  glucose  and  fructose 
of  levo-rotatory  character,  the  process  is  called  "inversion" 
and  the  product  "invert  sugar."  Such  is  not  the  case 
with  other  carbohydrates,  whose  products  remain  dex- 
tro-rotatory. 

The  tendency  to  crystallize  is  not  so  well  marked  in 
glucoses  as  in  the  sugars,  but  is  not  entirely  absent. 
Glucose  and  galactose  crystallize  readily  from  ordinary 
alcohol,  while  fructose  crystallizes  with  difficulty  from 
absolute  alcohol. 

Glucose  ferments  readily  with  yeasts  and  produces 
for  the  most  part  alcohol  and  carbon  dioxide  as  follows : 
C6H12O6=2GO2+2C2H5OH.  Fructose  is  less  readily 
fermented  but  yields  the  same  products.  In  the  case 
of  invert  sugar,  yeasts  attack  principally  the  glu- 
cose. Galactose  in  the  pure  state  is  not  attached  by  yeast 
but  when  mixed  with  glucose,  it  slowly  ferments.  The 
mixture  of  glucose  and  galactose,  obtained  by  hydro- 
lyzing  milk  sugar,  is  most  susceptible  to  the  action  of 


FOOD  PRINCIPLES  113 

lactic  acid  bacteria;  the  following  equations  explain  the 
change : 

CuHMOm  H20   =  2C0H1206. 

CCH1206=2C3H603. 

EXPERIMENTS  ON  GLUCOSE 

Note  the  taste  and  roughly  determine  the  solubility 
in  hot  and  in  cold  water.  Does  it  react  with  iodine 
solution  ? 

1.  Effect  of  Heat. — Heat  some  dry  glucose  in  a  clean 
dry  test-tube,  note  the  result. 

2.  Effect  of  Strong  Acid. — To  some  dry  glucose  in  a 
porcelain    dish    add    cold    concentrated    sulphuric    acid: 
note  the  result.     After  allowing  the  test  to  stand  for 
five  minutes,  heat  gently  and  again  note  the  result. 

3.  Effect  of  Strong  Alkali. — To  some  glucose  solution 
add  strong  caustic  soda  or  potash  and  heat;  note  the  re- 
sult. 

4.  Crystallization. — Make  a  syrupy  solution  of  glucose 
and  allow  it  to  stand  for  several  days.     Do  any  crystals 
form?  Add  an  equal  volume  of  95  per  cent,  alcohol,  mix 
well,  let  stand  twenty-four  hours.    What  result? 

5.  Fermentation. — Rub  up  some  glucose  solution  with 
a  small  piece  of  compressed  yeast  in  a  porcelain  mortar. 
Pour  the  mixture  into  a  short  broad  test-tube  until  it  is 
full  of  the  liquid.    Close  the  test-tube  with  a  perforated 
cork,  bearing  a  glass  tube  in  the  form  of  the  letter  J. 


114  HOUSEHOLD    CHEMISTRY 

The  short  end  of  the  tube  should  pass  through  the  cork 
into  the  broad  test-tube,  while  the  long  end  should  reach 
to  the  bottom  of  a  test-tube  containing  lime  water.  Set 
the  apparatus  away  in  a  warm  place,  and  allow  it  to 
stand  for  twenty-four  hours.  Why  does  the  limewater 
become  cloudy?  Examine  the  liquid  in  the  broad  tube 
for  alcohol  by  taste,  and  by  heating  with  a  few  drops 
of  iodine  and  sodium  carbonate  solution — the  odor  is 
that  of  iodoform. 

6.  Silver  Mirror  Test. — See  page  66. 

7.  Fehling's  Solution  Test. — In  a  100  cc.  flask  take  5 
cc.   of  copper  sulphate   solution   and   5   cc.   of   alkaline 
Rochelle  salt,  mix  and  add  20  cc.  of  distilled  water,  cover 
with   a  watch   crystal   and  boil   for   two   minutes.     No 
change  should  take  place.     Add  a  few  drops  of  glucose 
solution,  boil  vigorously  for  two  minutes,  cool  and  note 
the  result.     Continue  adding  glucose  and  boiling  until 
on  cooling  the  blue  color  of  the  solution  has  faded  and  a 
red  precipitate  is  formed.    Compare  with  Experiment  10 
under  starch.     It  requires  0.050  gram  of  glucose  to  re- 
duce the  Fehling's  solution. 

8.  Test  weak  glucose  solution  with  Nylander's  reagent 
under  the  same  conditions  as  observed  with   Fehling's 
Test.    Note  the  result. 

9.  Test    weak    glucose    solution    with    Barfoed's    rea- 
gent, heating  over  boiling  water.     Note  the  result. 


FOOD  PRINCIPLES  1 15 

10.  To  5  cc.  of  glucose  solution  in  a  test-tube  add  o.i 
gram  of  phenylhydrazine  hydrochloride  and  0.2  gram 
of  sodium  acetate.  Heat  the  mixture  gently  until  all 
solids  dissolve,  then  keep  it  in  boiling  water  for  fifteen 
minutes.  Cool  and  examine  the  yellow  radiating  needles 
of  phenylglucosazone. 

Examination  of  food  materials  (flours,  cereals,  bread, 
crackers,  etc.)  for  starch,  dextrine  and  glucose. 

Make  a  cold  water  solution  of  the  finely  ground 
material  to  be  tested ;  allow  to  stand  for  several  minutes, 
filter  through  starch-free  paper.  Test  the  residue  for 
insoluble  starch,  with  iodine.  Test  the  filtrate  (i)  for 
soluble  starch  and  dextrine  (a)  with  iodine.  (&)  With 
alcohol.  (2)  For  glucose  with  Fehling's  Test. 

SUGARS  (C12H220U) 

The  disaccharids  or  sugars  of  the  general  formula, 
C^HogOj!,  include  such  well  known  substances  as  suc- 
rose, maltose  and  lactose.  Unlike  the  glucoses  they  are 
not  identical  in  composition.  Sucrose  for  instance  is  an 
alcohol  with  no  trace  of  aldehyde  or  ketone  character 
as  shown  by  its  behavior  toward  Fehling's  reagent, 
while  maltose  and  lactose  possess  these  characteristics, 
reducing  the  reagent  in  marked  degree. 

The  sugars  are  readily  soluble  in  water  and  crystallize 
with  ease ;  facts  which  are  utilized  in  their  insolation.  On 
the  other  hand  they  hydrolyze  rapidly  at  low  temperatures 


Il6  HOUSEHOLD    CHEMISTRY 

with  all  acids,  hence  must  be  protected  by  neutralizing. 

CaAAi    +    H10==2C.H1?0.. 

Plants  accumulate  their  maximum  sugar  content  at  a 
period  just  short  of  maturity.  If  the  sap  is  decidedly 
acid,  little  sugar  will  be  found  in  the  mellow  stage,  the 
change  to  the  invert  form  being  almost  complete. 

SUCROSE  toAAi) 

Sucrose  is  identical  whether  separated  from  cane,  beets 
or  maple  juice. 

EXPERIMENTS 

1.  Examine   the   crystalline     structure   of   granulated 
sugar. 

2.  Roughly  determine  its  solubility  in  cold  water.     Is 
the  solubility  effected  by  heat? 

3.  Effect  of  Dry  Heat. — Boil  down  sugar  solution  to 
dryness  and  note  the  result. 

4.  Effect   of   Strong   Acid. — Drop   some   concentrated 
sulphuric  acid  on  dry  sugar,  note  the  result  and  compare 
with  starch  and  glucose. 

5.  Effect  of    Alcohol. — Add    a    saturated    solution  of 
sugar  to  95  per  cent,  alcohol  and  note  the  result. 

6.  Boil  weak  sugar  solution  with  Fehling's  solution. 
If  pure  there  should  be  no  reaction. 

7.  Hydrolysis  "Inversion/' — Boil   sugar  solution  with 
a   few   drops  of   concentrated   hydrochloric   acid,   cool, 
neutralize  with  sodium  carbonate  solution  and  heat  again 


FOOD  PRINCIPLES  117 

with  Fehling's  solution :  note  the  result  and  compare  with 
glucose.     What  change  has  taken  place? 

8.  Test  sugar  solution  with  Nylander's  reagent,  before 
and  after  boiling  with  acid. 

9.  Repeat  test  with  Barfoed's  reagent  as  in  Experiment 
9,  under  glucose. 

10.  Effect  of  Strong  Alkali. — To  10  cc.  of  sugar  solu- 
tion add  some  strong  caustic  potash,  heat  and  note  the  re- 
sult: compare  with  glucose. 

11.  Crystallization. — Make  a  hot   syrupy   solution  of 
sugar  and  suspend  in  it  a  piece  of  glass  rod  by  thread. 
Set  aside  and  allow  to  cool  and  after  a  time  carefully 
examine  the  crystals  of  cane-sugar. 

12.  Specific  Test. — To  15  cc.  of  the  clear  liquid,  add 
5  cc.  of  cobalt  chloride  (5  per  cent.)  and  2,  cc.  of  caustic 
soda  (50  per  cent.).     Sucrose  gives  an  amethyst-violet, 
permanent  on  heating.     Glucose  gives  a  turquoise-blue, 
turning  to  green  on  heating.     This  test  may  be  used  on 
milk,  preserves,  etc.     To  remove  gum  of  dextrine,  add 
ammonia  and  basic  acetate  of  lead,  filter  and  test  the 
filtrate. 

13.  Caramel  Test. — Boil  a  strong  solution  of  sugar  until 
it  has  turned  brown  (caramel),  cool,  dilute  and  test  some 
of  the  liquid  with  Fehling's  solution. 

14.  Saccharimeter  Test. — Certain  substances  when  dis- 
solved possess  the  power  of  rotating  the  plane  of  po- 


Il8  HOUSEHOLD    CHEMISTRY 

larized  light,  some  to  the  right,  others  to  the  left.  Cane- 
sugar  is  dextro-rotatory.  For  the  saccharimeter  test 
(using  the  Ventzke  scale)  16.37  grams  of  cane-sugar 
are  dissolved  in  the  least  quantity  water  and  made  up  to 
loo  cc.  The  tube  of  the  instrument  is  then  filled  with 
the  solution  and  the  percentage  of  sugar  read  directly 
on  the  graduated  scale  of  the  instrument. 

After  making  the  first  reading,  dilute  some  of  the 
solution  with  an  equal  volume  of  water  and  make  another 
reading  on  this  solution. 

For  the  saccharimeter  test,  the  solution  must  be  clear 
and  colorless.  In  case  it  is  not,  the  color  may  be  dis- 
charged by  means  of  a  solution  of  basic  acetate  of  lead, 
which  precipitates  dextrine  and  gummy  matter,  and  by 
bone-black,  which  removes  soluble  coloring  matter.  The 
operation  is  conducted  as  follows: — 16.37  grams  of  sugar 
are  dissolved  in  somewhat  less  than  100  cc.  water,  a 
few  cc.  (not  more  than  five)  of  the  lead  solution  are 
added  and  the  solution  diluted  to  mark.  The  mix- 
ture is  shaken  vigorously  and  then  allowed  to  stand 
for  a  few  minutes  for  the  bulky  precipitate  to  settle. 
If  perfectly  clear  and  colorless,  the  liquid  is  poured  into 
the  tube;  if  the  color  has  not  entirely  been  removed 
a  subsequent  treatment  with  bone-black  is  necessary. 
For  this  purpose  bone-black  which  has  been  dried  at 
a  red  heat  is  mixed  with  the  solution  and  stirred  for  some 
minutes.  The  mixture  is  then  filtered  through  dry 


FOOD  PRINCIPLES  IIQ 

paper,  the  first  10  cc.  of  the  filtrate  being  rejected. 
It  may  be  necessary  to  refilter  the  liquid  through  the 
same  paper  two  or  three  times. 

MALTOSE  (C12H22On) 

Maltose  does  not  occur  in  nature,  but  is  produced 
during  the  hydrolysis  of  starch  by  unorganized  ferments, 
such  as  diastase,  ptyalin,  etc. 

Preparation  of  Malt. — Malt  is  produced  during  the 
germination  of  barley  and  other  cereals.  Prepare  it  as 
follows:  spread  out  a  thin  layer  of  barley  grains  (one 
tablespoonful)  on  the  cover  of  a  small  pasteboard  box, 
moisten  with  warm  water  and  keep  in  a  moderately  warm 
place.  Each  grain  will  soon  begin  to  sprout.  When  the 
rootlet  has  grown  the  length  of  the  grain,  dry  it  in  an 
oven  at  a  low  temperature  and  keep  bottled. 

Make  malt  extract  by  grinding  the  grains  coarsely  and 
extracting  them  with  100  cc.  of  warm  water.  Note  the 
taste  and  odor  of  the  liquid.  Keep  for  future  use. 

Preparation  of  Pure  Maltose. — Make  a  thin  paste  of 
starch  and  boiling  water,  cool  to  65°  C.  and  add  100  cc.  of 
malt  extract,  prepared  as  above,  and  continue  the  heat-* 
ing  at  65°  C.  for  half  an  hour.  From  time  to  tm«e  test 
small  portions  of  the  liquid  with  iodine  solution.  When 
the  liquid  fails  to  react  blue,  the  balance  of  the  solution, 
divide  in  parts  and  test  as  follows: 

1.  Solubility  in  Alcohol.— Add  some  of  the  liquid  to 


I2O  HOUSEHOLD    CHEMISTRY 

strong  alcohol,  allow  to  stand  and  note  the  white  pre- 
cipitate of  dextrine :  the  liquid  contains  maltose. 

2.  Effect  of  Fehling's  Solution. — To  10  cc.  of  Fehling's 
solution  add  a  few  drops  of  the  liquid,  boil  for  two  min- 
utes and  note  the  reduction ;  add  more  of  the  solution 
and  boil  again:  repeat  until  the  reduction  is  complete. 
The  solution  is  reduced  by  0.08  gram  maltose. 

3.  Effect  of  Barfoed's  Reagent. — Test  with  Barfoed's 
reagent. 

4.  Effect  of  Nylander's  Keagent. — Test  with  Nylander's 
reagent. 

5.  Apply  the  fermentation  test. 

6.  Test  with  strong  caustic  soda  or  potash. 

7.  Repeat   the   phenylhydrazine   test.      Compare   with 
glucose. 

LACTOSE  (C^Ai,  S2<>) 

Method  of  Preparation. — Allow  milk  to  stand  until  it 
has  become  decidedly  sour,  filter.  Heat  the  whey  to 
coagulate  the  albumen,  filter  again.  Evaporate  the  fil- 
trate over  hot  water,  to  crystallization.  The  crystals  are 
lactose. 

1.  Note  the  hardness  and  slightly  sweet  taste,  due  to 
the  limited  solubility. 

2.  Try  its  solubility  in  water  and  in  alcohol. 

3.  Treat  some  dry  powdered  lactose  with  concentrated 
sulphuric  acid  note  the  result. 


FOOD  PRINCIPLES  121 

4.  Try  the  caustic  potash  reaction. 

5.  Apply  the  Fehling's  test.     It  requires  0.068  gram 
to  reduce  the  solution. 

6.  Test  with  Barfoed's  reagent. 

7.  Test  with  Nylander's  reagent. 

8.  Make  a  weak  solution  of  lactose  in  water,  let  it 
stand  at  least  twenty-four  hours  in  a  moderately  warm 
place,  and  then  test  for  acidity. 

9.  Make  the  phenylhydrazine  test,  compare  with  glucose 
and  maltose. 


Chapter  X 


METHODS  FOR  TESTING  FLOURS,  MEALS,  ETC. 

Samples  to  be  tested:  viz.,  white  bread,  baker's,  mac- 
aroni and  whole  wheat  flour. 

Examine  small  portions  of  each  under  the  microscope 
as  in  lesson  under  starch.  Make  paste,  stain  with  iodine 
and  examine  again. 

1.  Preparation  of  Gluten. — Take  25  grams  of  the  sam- 
ple, mix  on  a  porcelain  or  glass  plate  with  the  least 
amount  of  water  to  make  a  stiff  dough  (12-15  cc.).  Do 
not  handle  the  dough  with  the  fingers,  use  a  flexible  steel 
knife.  Transfer  the  dough  to  a  well-washed  piece  of 
muslin,  taking  care  to  clean  the  mixing  surface  and 
knife  thoroughly;  tie  up  the  muslin  in  the  form  of  a 
bag  and  wash  under  a  gentle  stream  of  water,  manipu- 
lating well  with  the  fingers.  Continue  the  washing  until 
the  liquid  runs  clear  from  the  bag,  and  fails  to  give  the 
test  for  starch  with  iodine.  Be  careful  to  collect  all 
the  washings  in  a  tall  glass  beaker  or  jar — (they  should 
amount  to  from  one  to  one  and  a  half  liters).  Strain 
through  muslin  and  stand  the  filtrate  aside  in  a  cool 
place  for  settling.  Reserve  for  future  use.  Examine 
the  residue  with  a  lens.  Squeeze  out  as  much  water  as 
possible  from  the  bag,  untie  it  and  collect  and  weigh  the 


METHODS  FOR  TESTING  FLOURS,  MEATS,  ETC.         123 

moist  gluten ;  spread  it  out  in  a  thin  cake  and  dry  it  for 
one  hour  at  ioo°-io5°  C.  Cool  and  weigh  the  dry  gluten. 

2.  Tests  on  Protein  and  Soluble  Carbohydrates. — When 
the  contents  of  the  jar  (used  in  last  experiment)  have 
settled,  decant  off  the  clear  liquid,  and  test  small  por- 
tions of  it  for  protein  with  the  Biuret  test  and  for  solu- 
ble carbohydrate  with  Fehling's  reagent. 

Note.  Biuret  Test — To  I  in.  of  10  per  cent.  NaOH 
or  KOH,  add  very  dilute  CuSO4  solution,  drop  by  drop, 
until  a  faint  blue  color,  but  no  precipitate  appears  in  the 
liquid.  Now  add  the  protein  solution — a  violet  color 
indicates  protein,  a  pink  peptone. 

3.  Tests  on  Starch. — Pour  distilled  water  on  the  residue 
in  the  jar  and  stir  up  the  mixture,  allow  it  to  settle  and 
decant  as  before.     Repeat  this  operation  twice,  and  then 
collect  the   residue  on  balanced  filter-papers ;  dry  and 
weigh.     This  last  weight  gives  the  starch  and  fiber  con- 
tent but  in  the  case  of  ordinary  wheat  flours  the  latter 
is  so  small  that  it  may  be  neglected. 

Note — In  the  case  of  a  whole  wheat  flour  it  is  best  to 
pass  the  sample  through  a  loo-mesh  sieve,  taking  the 
screenings  for  the  determination  of  starch,  gluten,  etc. 

4.  Determination  of  Ash. — Incinerate  about  5  grams  of 
the  sample  in  a  porcelain  dish,  cool,  and  moisten  the 
ash  with  a  few  drops  of  concentrated  nitric  acid.     Add 
water,   boil    and   filter.     Test   the   filtrate    (i)    for   po- 

9 


124  HOUSEHOLD    CHEMISTRY 

tassium  with  platinic  chloride   (2)   for  phosphoric  acid 
with   ammonium  molybdate. 

Rye  Flour. — Examine  under  the  microscope  as  under 
wheat  flour.  Take  25  grams  of  rye  flour  and  pass  it 
successively  through  screens  of  40,  60,  80  and  loo-mesh ; 
weigh  and  examine  the  residue  retained  by  each  sieve  and 
also  test  them  for  starch  with  iodine.  Treat  the  ma- 
terial which  has  passed  the  loo-mesh  sieve  for  the  de- 
termination of  starch,  gluten,  etc.,  as  described  under 
wheat  flour. 

Ash  a  small  portion  and  determine  the  mineral  constit- 
uents as  under  wheat  flours. 

Corn  Meal  (Yellow). — Examine  under  the  microscope 
as  before.  Test  a  small  portion  in  a  corked  test-tube 
with  ether  or  benzine;  shake  vigorously  and  when  the 
upper  layer  of  liquid  is  clear,  decant  it  through  a  filter- 
paper  and  cautiously  evaporate  the  liquid  in  a  clean,  dry 
evaporating  dish.  Note  the  character  of  the  residue: 
What  is  it? 

Treat  about  25  grams  for  the  determination  of  starch, 
protein,  etc.,  as  before. 

Make  ash  determination  as  before. 

Experiments  on  Raw  Potatoes. — i.  Select  a  small  sound 
potato,  clean  well  and  carefully  grate  it  over  a  shallow 
tin  dish.  Allow  a  thin  stream  of  water  to  play  upon  the 
grater  during  the  operation;  not  more  than  one  quart 


METHODS  FOR  TESTING  FLOURS,  MEATS,  ETC.         125 

of  water  should  be  used.  Pour  the  gratings  and  liquid 
through  a  muslin  strainer  into  a  tall  glass  jar  and  allow 
the  contents  to  settle.  Examine  some  of  the  material  on 
the  filter  with  a  lens,  and  test  it  with  iodine. 

2.  When  the  contents  of  the  jar  have  settled,  draw 
off  some  of  the  clear  liquid  and  test  for  protein  and 
soluble  carbohydrate. 

3.  Test  the  settlings  for  starch. 

Note. — To  preserve  these,  wash  several  times  with 
dilute  salt  solution,  drain  and  dry  at  a  low  temperature. 

Experiments  on  Cooked  Potatoes. — i.  Take  a  small  well 
baked  potato.  Remove  and  dry  the  skin,  grind  in  a  mill 
and  test  the  clear  water  solution  and  the  insoluble  resi- 
due for  starch,  protein  and  mineral  matter. 

2.  Examine  the  white  interior  of  the  potato  for  un- 
cooked starch  grains,  with  a  microscope. 

3.  Make  a  solution  of  a  portion  of  this  material,  filter 
and  subject  to  the  same  tests  as  used  on  the  skin. 

Experiments  on  Bread. — Separate  the  crumb  and  crust. 

Crust. — Grind  the  darker  portion  to  a  coarse  powder, 
add  water  and  mix  thoroughly.  Add  more  water,  boil 
the  mass  for  some  time,  cool  and  filter.  Divide  the 
filtrate  into  four  parts  and  test  as  follows: 

1.  Add  iodine  solution  and  note  the  result. 

2.  Observe  the  taste;  explain. 

3.  Add  to  Fehling's  solution  and  boil;  note  the  re- 
sult. 


126  HOUSEHOLD    CHEMISTRY 

4.  Pour  a  few  drops  into  strong  alcohol. 
Crumb. — Test  the  crumb  as  follows : 

1.  Add  iodine  solution  and  note  the  result. 

2.  Make  test  for  insoluble  protein   (gluten).     Which 
test  is  best? 

3.  Burn  some  crumb  to  a  gray  ash  in  a  porcelain  dish, 
cool,  digest  ash  with  warm  nitric  acid  and  divide  into 
three  parts.     Test  one  part  for  chlorides,  another  for 
phosphates  and  the  remainder  for  potassium. 

Experiments  on  Toast. — Grind  toast  to  powder,  treat 
one  teaspoonful  (level)  with  boiling  water  for  five  min- 
utes, filter  hot,  cool.  Divide  liquid  into  four  parts  and 
test  as  follows: 

1.  With  iodine  solution. 

2.  With  Fehling's  solution. 

3.  With  tannic  acid. 

4.  Add  a  few  drops  of  the  cooled  liquid  to  strong 
alcohol. 

Experiments  on  "Cereals  or  Breakfast  Foods.1' — This 
classification  includes  the  various  commercial  prepara- 
tions of  oats,  corn,  barley,  wheat  and  rice,  or  mixtures 
of  the  same.  They  are  supposed  to  have  undergone 
some  operation  of  cooking  and  claim  to  contain  no  raw 
starch.  The  following  general  tests  will  serve  to  give 
some  idea  as  to  the  condition  of  the  material  and  the 
presence  or  absence  of  the  various  food  principles: 


METHODS  FOR  TESTING  FLOURS,  MEATS,  ETC.         I2/ 

1.  Powder  the  material  as  finely  as  possible  in  a  mor- 
tar or  coffee-mill.     Pass   the  grinding  through  a   100- 
mesh  sieve  and  examine  the  screenings  and  siftings  sep- 
arately under  the  microscope.     Stain   with  iodine  and 
examine  for  the  presence  of  unbroken  starch  grains. 

2.  Extract  a  portion  of  both  screenings  and  siftings 
with  cold  water,  filter  and  examine  the  filtrates  separate- 
ly for  dextrine — (by  precipitation  with  alcohol  and  color 
test  with  iodine),  for  glucose  or  reducing  sugars  (with 
Fehling's  solution),  for  maltose  (with  phenylhydrazine). 

3.  Test  portions   of  the   insoluble   residue   separately 
for  protein. 

4.  Mineral  Matter. — Incinerate  a  fresh  portion  of  the 
screenings  in  a  porcelain  dish,  cool  and  extract  the  mass 
with  water,  filtering  and  testing  the  filtrate  for  chlorides, 
sulphates  and  phosphates  of  potassium  and  sodium.  Test 
the  insoluble  residue  with  a  little  concentrated  nitric  acid 
and   boil.     Cool,   dilute   with  water,   filter  if  necessary 
and  test  the  clear  liquid  for  phosphates  and  for  calcium. 


Chapter  XI 

FATS  AND  OILS 

There  is  much  confusion  in  regard  to  the  composition 
of  the  various  bodies  commonly  known  as  fats. 
At  least  two  distinct  classes  are  recognized,  viz. 

(1)  True   fats  or  glycerides,   containing  carbon  hy- 
drogen and  oxygen,  essentially  in  the  form  of  fatty  acid 
and  glycerine,  and  existing  as  solids  and  liquids. 

(2)  Hydrocarbons  containing  only  carbon  and  hydro- 
gen  in  varied    forms  of  combination,  but   existing  as 
gases,  liquids  and  solids. 

On  heating  the  first  always  yield  some  of  their  carbon 
in  the  free  state,  the  latter  rarely. 

Ordinarily  fats  consist  of  mixtures  of  at  least  three 
glycerides;  oleine,  liquid  at  ordinary  temperatures,  pal- 
mitine  semi-solid  and  stearine  solid.  In  very  few  in- 
stances other  glycerides  are  present,  notably  butter, 
cocoanut  oil,  cotton  oil,  etc.  Hence  olive  oil  is  liquid 
because  of  the  preponderance  of  oleine  and  tallow  hard 
from  excess  of  stearine. 

In  fact  these  mixtures  are  separable  by  heating  or 
cooling  them  to  a  temperature  just  short  of  solidification 
or  liquefaction  and  pressing  the  mass. 

Fats  and  oils  are  insoluble  in  hot  and  cold  water ;  solu- 


FATS  AND  oii^s  129 

ble  in  hot  alcohol  and  in  cold  and  hot  ether,  chloroform 
and  gasoline. 

The  radicle  glyceryl  (C3H6)'"  is  common  to  all  fats, 
the  fatty  acid  may  vary. 

In  the  process  of  saponification  (fat  splitting)  gly- 
cerine C3H5(OH)3  is  therefore  a  constant  product. 

(C17HSBCOO),C,HB  +  3HOH  =  3C17H35COOH  + 
C3H5(OH)3,  ultimate  composition  of  glycerides. 

Determination  of  Hydrogen  and  Oxygen  in  the  Form  of 
Water. — Boil  20-25  drops  of  clear  olive  oil  in  a  clean 
dry  test-tube.  Note  the  watery  deposit  in  the  cooler  part 
of  the  tube;  some  of  this  running  back  will  cause  the 
fat  to  crackle. 

Determination  of  Glycerine. — Continue  heating  the  tube 
until  dense  fumes  arise  from  the  boiling  liquid.  This 
is  due  to  acrolein  C3H4O  a  decomposition  product  of 
glycerine. 

C3H803:=C3H40+2HB0. 

Cool  the  tube  and  contents  and  reserve  for  next  step. 

Determination  of  Carbon  and  Hydrogen  as  Hydrocar- 
bons Resulting  from  the  Break  Down  of  the  Fatty  Acids. 
— Pour  the  cold  tube  contents  into  a  clean  dry  porcelain 
dish  and  heat  slowly  but  strongly  over  a  low  flame. 
Note  the  gradual  darkening  of  the  liquid  due  to  freeing 
of  carbon  and  the  tarry  coat  on  the  rim  of  the  dish  (hy- 
drocarbons). Hold  a  lighted  match  over  the  dish  and 


I3O  HOUSEHOLD    CHEMISTRY 

note  the  inflammable  character  of  the  vapor  (hydrocar- 
bon gases).  Extinguish  the  flame  and  continue  the  heat- 
ing until  only  a  black  residue  remains.  This  is  carbon: 
prove  it  by  burning  off. 

Extraction  of  Pure  Fat  from  Animal  Sources. — Weigh 
out  10  grams  of  beef  suet  cut  up  in  small  pieces.  Place 
in  a  small  evaporating  dish  and  heat  cautiously,  stir  with 
a  thermometer  and  do  not  allow  the  temperature  to  rise 
above  130°  C.  (What  causes  the  spattering?)  When 
the  spattering  has  ceased,  strain  through  muslin  into 
a  porcelain  dish,  squeeze  out  the  cloth  and  reserve  con- 
tents for  tests  on  fats. 

Transfer  the  residue  to  a  small  mortar,  add  5  cc.  of 
strong  alcohol,  grind  well.  Pour  this  mixture  into  a 
small  flask,  wash  out  the  mortar  with  alcohol  and  add 
the  washings  to  the  flask.  Finally  close  the  flask  with 
a  cork,  bearing  a  condenser  tube  24  inches  long,  support 
on  a  ring  stand  over  a  water-bath  and  boil  for  ten  min- 
utes. When  the  suspended  matter  has  settled,  uncork 
the  flask  and  pour  the  clear  liquid  on  a  small  filter,  al- 
lowing the  filtrate  to  run  into  a  large  test-tube.  To  the 
residue  in  a  flask,  add  20  cc.  of  ether,  insert  the  cork  and 
condenser  and  cautiously  heat  over  hot  water  for  five 
minutes.  Then  transfer  the  entire  contents  of  the  flask 
to  a  small  muslin  filter  and  collect  the  filtrate  in  the 
same  tube  as  before.  Wash  this  last  residue  with  a 
little  ether,  squeeze  out,  spread  on  the  muslin  and  allow 


FATS  AND  OILS  131 

it  to  dry.  Test  the  residue  for  protein  with  Millon's 
reagent.  Close  the  test-tube  with  a  loose  cotton  plug, 
allow  it  to  stand  until  crystals  deposit  from  the  liquid. 
Examine  these  under  the  microscope  and  draw  a  diagram 
of  them. 

Extraction  of  Pure  Fat  from  Seeds  or  Nuts. — Dry  and 
grind  the  nuts  to  a  fine  powder.  Place  the  ground  mass 
in  a  small  Erlenmeyer  flask,  cover  with  the  solvent 
(ether),  cork  and  shake  well.  Remove  the  cork  and 
heat  very  gently  over  warm  water.  Finally  pour  the 
clear  liquid  through  a  dry  filter  into  a  clean  porcelain 
dish  and  cautiously  drive  off  the  solvent.  The  clear  oily 
residue  is  used  for  tests. 

-Make  the  following  tests  on  the  rendered  (extracted) 
fat: 

1.  Solubility. — Test  the  solubility  of  small  portions  of 
fat  in  separate  test-tubes  with  water  hot  and  cold,  al- 
cohol hot  and  cold.     Record  the  results. 

2.  Acidity  (Rancidity). — Place  a  small  piece  of  fat  in 
a  clean,  dry  test-tube;  add  5  cc.  of  neutral  alcohol  and 
heat  until  the  fat  melts,  cool  and  test  the  liquid  with 
delicate  litmus  paper. 

3.  Absorption.- — Place  a  small  piece  of  fat  on  a  filter- 
paper  and  heat  until  the  fat  melts;  note  the  result. 

4.  Formation  of  Acrolein. — Rub  up  a  small  piece  of 
fat  in  a  mortar  with  some  acid  potassium  sulphate,  trans- 


132  HOUSEHOLD    CHEMISTRY 

fer  to  a  clean,  dry  test-tube  and  heat  cautiously;  note 
the  peculiar  disagreeable  odor  of  acrolein  due  to  the 
dehydration  of  the  glycerine.  What  does  it  suggest? 

5.  Solubility  in  Na2C03. — Warm  a  small  piece  of  fat 
in  a  test-tube  with  strong  Na2CO3,  shake  well,  noting 
the  result.     Allow  the  mixture  to  stand:  what  happens? 

6.  Saponification  with  Alkali. — To  about  i  gram  of 
fat  in  a  low  flask  fitted  with  a  reflux  condenser  add  25 
cc.  of  alcoholic  potash  solution  and  boil.     Replace  the 
liquid  lost  by  evaporation  with  alcohol.     As  the  heating 
progresses,  the  mixture  should  become  homogeneous;  if 
it  does  not,  add  a  little  more  potash  and  boil  until  clear 
(saponified).     Remove  the  cover  and  evaporate  the  bulk 
of  the  alcohol,  finally  adding  hot  water  and  heating  until 
all  alcoholic  odor  has  disappeared.     Cool  the  liquid  and 
divide  into  three  parts. 

7.  Precipitation  and  Decomposition  of  Soap. — To  one 

portion  add  a  saturated  solution  of  salt ;  notice  the  curdy 
precipitate  (soap).  Filter  off  this  precipitate,  try  its 
solubility  in  cold  water.  Boil  down  some  of  the  filtrate, 
note  any  change  in  color  or  odor  and  finally,  when  quite 
concentrated  pour  a  few  drops  of  the  thick  liquid  on  a 
platinum  foil,  add  acid  potassium  sulphate  evaporate 
to  dryness  and  ignite  gently.  Note  the  odor  and  black- 
ening; what  does  it  suggest?  (Odor  of  frying  fat.) 
What  are  the  white  crystals? 


FATS    AND    OILS  133 

8.  Separation  of  Fatty  Acids. — Acidify  another  portion 
of  the  dissolved  soap  with  dilute  sulphuric  acid.     Note 
the  curdy  precipitate  (fatty  acids)  which  is  insoluble  in 
water  but  soluble  in  warm  alcohol.     Boil  the  mixture 
until  clear,  filter  and  use  in  test  9. 

9.  Test  the  solubility  of  the  fatty  acids  with  alcohol 
and  with  sodium  carbonate  solution.     Record  results. 

10.  Formation  of  Lime  Soap. — Add  a  solution  of  lime- 
water  to  another  portion  of  the  soap  solution  and  notice 
the  greasy  precipitate,  which  is  insoluble  in  warm  water 
and  alcohol   (lime  soap,  produced  by  hard  water). 

11.  Emulsification. — Shake  together  a  few  centimeters 
of  cod-liver  oil  and  dilute  sodium  carbonate.     Notice  the 
resulting  white  mass  which  is  called  an  emulsion;  what 
well  known  liquid  is  similar  in  appearance?     Examine 
two  or  three  drops  of  this  emulsion  under  the  micro- 
scope and  note  the  character  of  the  compound. 

Repeat  the  same  experiment,  using  a  few  drops  of 
olive  oil  and  a  solution  of  albumen. 

12.  Formation  of  Lead  Soap. — Heat  a  small  quantity 
of  lard  or  tallow,  for  some  time  in  an  evaporating  dish, 
with  lead  oxide  PbO,  and  a  little  water;  filter  off  the 
watery  liquid  and  evaporate  a  small  quantity  on  a  plati- 
num foil.     Note  the  characteristic  odor  of  acrolein,  prov- 
ing the  presence  of  glycerine. 

13.  Melting-points  (Lard  Olive  or  Cottonseed  Oil,  Tal- 
low).— Determine  the  melting-point  by  filling  capillary 


134  HOUSEHOLD    CHEMISTRY 

tubes  with  the  respective  liquid  fats.  Chill  them  with 
cracked  ice  and  salt,  and  fasten  to  the  bulb  of  a  chemi- 
cal thermometer  with  a  small  rubber  band.  Immerse  this 
system  in  a  beaker  of  cool  water  and  gradually  raise  the 
temperature  (not  faster  than  2°  C.  per  minute).  When 
the  contents  of  the  tubes  become  translucent,  the  melt- 
ing-point has  been  reached.  Record  results  in  each 
case. 

14.  Special  Tests  for  Drying  Oils. — (a)  Becchi's  Test. 
— To  5  cc.  of  the  oil  in  a  4-inch  test-tube,  add  an  equal 
volume  of  silver  nitrate  dissolved  in  alcohol  ( i  per  cent, 
solution)  ;  close  the  test-tube  with  a  cotton  plug  and 
keep  it  in  boiling  water  for  ten  to  fifteen  minutes.  A 
darkening  of  the  mixture  indicates  cotton-seed  oil. 

(b)  Halphen's  Test. — To  5  cc.  of  the  oil  in  a  6-inch 
test-tube  add  5  cc.  of  amyl  alcohol  and  5  cc.  of  carbon 
disulphide  containing  a  little  free  sulphur.  Close  the 
test-tube  with  a  loose  cotton  plug  and  keep  in  hot  water 
away  from  an  open  flame  for  a  half  hour.  A  red  colora- 
tion indicates  cotton-seed  oil.  This  is  a  very  delicate 
test. 

(c~)  Drying  Test. — Expose  separate  drops  of  olive  and 
cotton-seed  oils  on  a  microscope  slide  to  a  warm  dry 
atmosphere  for  12-24  hours.  Cool  and  note  any  differ- 
ence in  character. 


FATS    AND    OILS  135 

PREPARATION  OF  COLD-MADE  SOAP 

Lye. — Dissolve  the  contents  of  one  can  of  Babbitt's 
potash  (i  Ib.)  in  one  quart  of  cold  water.  This  gives 
a  solution  of  about  40°  Be. 

Fat. — Tallow  rendered  according  to  directions  given 
on  page  130.  Heat  the  fat  until  it  is  just  liquid  and  add 
slowly,  with  constant  stirring,  lye  equal  in  amount  to 
one-half  the  fat  taken.  Stir  it  thoroughly  until  homo- 
geneous and  pour  into  a  shallow  pasteboard  box.  Al- 
low it  to  stand  for  at  least  twenty-four  hours,  and  then 
test  for  free  fat  and  free  alkali  as  follows: 

For  Free  Fat. — Shake  a  few  shavings  of  the  soap  in 
a  corked  test-tube  with  cold  gasoline,  filter  into  a  convex 
glass  and  evaporate  off  the  gasoline  over  warm  water. 
A  greasy  residue  indicates  unsaponified  fat. 

For  Free  Alkali. — Shake  a  few  shavings  of  the  soap 
in  a  corked  test-tube  with  warm  alcohol  (95  per  cent.), 
filter  and  add  to  the  clear  liquid  a  few  drops  of  phenol- 
phthalein;  a  red  color  indicates  free  alkali. 

BUTTER.    SPECIFIC  TESTS 

Melt  about  a  teaspoonful  of  butter  with  ten  times  the 
volume  of  warm  water,  stir  the  mixture  vigorously  and 
then  chill  by  standing  it  in  ice-water.  Punch  two  holes 
in  the  cake  of  solid  fat  and  decant  off  the  liquid.  Pre- 
serve some  of  this  liquid  for  a  test.  Taste  a  portion; 
test  with  litmus  paper.  To  a  small  portion  of  the  solu- 


136  HOUSEHOLD    CHEMISTRY 

tion  add  a  few  drops  of  silver  nitrate  and  note  the  result. 
Continue  the  washing  operation  two  or  three  times  until 
the  final  filtrate  is  quite  clear.  Note  any  difference  be- 
tween the  first  and  last  filtrates  in  respect  to  taste,  and 
test  with  litmus  and  silver  nitrate.  Carefully  dry  some 
of  the  chilled  fat  between  layers  of  filter-paper.  Melt 
the  fat  in  hot  water  and  filter  it  through  dry  paper.  Pre- 
serve this  fat  for  future  work. 

Now  wash  the  paper  with  a  very  small  portion  of  cold 
gasoline  until  a  drop  of  the  washings  evaporated  on 
paper  leaves  no  greasy  stain,  dry  and  note  the  character 
of  the  residue  on  the  filter-paper.  Cautiously  heat  some 
of  the  residue  (curd)  in  a  test-tube  with  lime;  observe 
the  odor  produced  and  hold  in  the  fumes  a  piece  of 
moistened  red  litmus  paper  and  note  the  result. 

Place  a  drop  of  the  butter-fat  first  on  water  and  then 
on  95  per  cent,  alcohol;  note  whether  it  floats  or  sinks 
in  either  liquid.  Mix  a  small  portion  of  the  fat  with 
potassium  acid  sulphate  heat  on  a  platinum  foil,  and 
note  the  peculiar  disagreeable  odor  (acrolein).  Com- 
pare the  odor  of  this  compound  with  the  odor  produced 
by  treating  glycerine  in  the  same  way. 

Spoon  Test. — Heat  a  piece  of  butter  about  the  size  of  a 
cherry  in  a  tablespoon.  If  it  froths  without  spattering, 
it  is  pure  butter.  If  it  foams  and  spatters  it  is  renovated 
butter;  if  it  spatters  only,  it  is  olemargarine  or  some 
other  artificial  butter. 


FATS    AND    OILS  137 

Butyric  Acid  Test. — In  a  4  oz.  narrow  neck  flask,  fitted 
with  a  one-holed  rubber-stopper,  put  about  2^  grams  of 
butter.  Saponify  with  caustic  potash.  Decompose  the 
resulting  product  with  dilute  sulphuric  acid  in  excess. 
Then  distill  the  product  gently,  using  a  bent  tube  con- 
denser. Butyric  acid  will  distill  at  about  the  temperature 
of  boiling  water.  Allow  the  distillate  to  drop  into  a 
funnel  containing  moist  filter-paper.  This  causes  the  re- 
tention of  fatty  acids  (other  than  butyric).  Below  the 
funnel  is  placed  an  Erlenmeyer  flask  containing  N/io 
alkali,  with  phenolphthalein  as  indicator.  The  excess  of 
alkali,  after  the  distillation  is  complete,  is  titrated  with 
N/io  HC1. 


Chapter  XII 


PROTEIN  BODIES 

These  compounds  contain  carbon,  hydrogen,  oxygen 
and  nitrogen,  sometimes  sulphur,  phosphorus,  iron,  lime, 
etc. 

They  may  be  classed  as  follows: 

j  Albumens. 
Simple  <   Globulins. 
Proteins  j  I  Sclero-proteins. 

v^onipound  * 

(  Conjugated-protems. 

The  ultimate  composition  of  the  proteins  may  be  de- 
termined as  follows: 

1.  Determination  of  Nitrogen  as  Ammonia. — Mix  some 
dried  egg  albumen  with  lime  and  moisten   sufficiently 
to  roll  into  small  balls  with  the  fingers.     Place  two  or 
three  of  these  balls  in  a  dry  test-tube,  heat  and  hold 
in  the  vapors  a  piece  of  moistened  red  litmus  paper. 
Note  the  result.     Let  the  paper  dry  and  observe  the 
change. 

2.  Determination  of  Sulphur  as  Hydrogen  Sulphide. — 
Test  the  fumes  with  a  piece  of  filter-paper  moistened 
with  lead  acetate  and  note  the  result. 


PROTEIN    BODIES  139 

3.  Determination  of  Hydrogen  and  Oxygen  as  Water. — 
Observe  the  condensation  of  water  in  the  cooler  part  of 
the  tube. 

4.  Determination  of  Carbon. — Observe  the  blackening 
effect  produced  by  the  freeing  of  the  carbon. 

5.  Determination  of  Phosphorus. — Moisten  the  residue 
from  test  4  with  concentrated  HNO3  and  heat  gently 
until  excess  of  acid  has  been  vaporized,  then  heat  strong- 
ly until  the  carbon  has  been  entirely  consumed.     Cool 
the  residue,  moisten  with  HNO3,  add  water,  boil  and 
filter  if  necessary.     Test  the  clear  liquid  with  ammonium 
molybdate. 


1.  Solubility. — Albumens   and  gelatine  are  soluble  in 
warm  water,  other  forms  are  insoluble. 

All  proteins  are  soluble  in  dilute  sodium  chloride,  al- 
bumens alone  are  soluble  in  saturated  solutions. 

All  proteins  are  insoluble  in  saturated  solutions  of 
ammonium  sulphate. 

Make  a  table  based  on  these  facts. 

2.  Coagulation. — Albumens    and    globulins    are    made 
insoluble  by  heating  their  neutral  or  faintly  acid  solu- 
tions to  about  70°  C. 

3.  Curdling. — Phospho-   and   conjugated   proteins   are 
made    insoluble,    without    serious    chemical    change,  by 
adding  dilute  acid. 

10 


I4O  HOUSEHOLD    CHEMISTRY 

4.  Clotting. — Certain  enzymes  (rennin)  split  phospho- 
and  conjugated  proteins,  yielding  nuclein  and  simple  pro- 
tein. 

5.  All  proteins  are  insoluble  in  alcohol. 

6.  Proteins  are  indiffusible. 

7.  Proteins  hydrolyze  and  yield  the  following  prod- 
ucts; meta-protein   (acid  or  alkali)  proteoses,  peptones 
and  polypeptides   (amino  acids). 

For  the  purpose  of  making  general  and  specific  tests 
on  the  proteins,  a  solution  of  egg  albumen  prepared 
according  to  the  following  directions  is  recommended. 

Preparation  of  Egg  Albumen. — Carefully  break  a  fresh 
egg,  allow  the  clear  white  to  run  into  a  porcelain  dish 
and  set  the  yolk  aside  for  future  use.  Cut  the  white 
with  scissors  or  grind  with  sand  and  place  a  small  por- 
tion in  a  wide-mouthed  stoppered  bottle,  add  ten  vol- 
umes of  distilled  water,  shake  until  it  froths  and  invert 
over  a  small  casserole  of  water.  When  the  froth  and 
insoluble  protein  particles  float  on  the  surface,  carefully 
withdraw  the  cork  and  allow  some  of  the  liquid  to  mix 
with  the  water  in  the  casserole.  The  liquid  will  prob- 
ably be  opalescent,  due  to  traces  of  globulin;  if  strongly 
so  filter  through  cloth,  test  the  fluid  with  litmus  paper 
and  if  alkaline  neutralize  with  weak  acetic  acid  (2  per 
cent. ) . 

i.  General  Tests. — (a)  Nitric  Acid. — To  a  small  por- 


PROTEIN    BODIES  141 

tion  of  the  filtered  liquid,  add  strong  nitric  acid.  This 
forms  a  white  precipitate  which  turns  yellow  on  heat- 
ing; now  cool  and  add  ammonia — it  becomes  orange. 
Compare  with  spots  on  the  skin  or  woolen  cloth  produced 
with  HNO3. 

(b)  Biuret  Test. — To  I  inch  of  10  per  cent,  caustic 
soda  or  potash,  add  dilute  copper  sulphate,  drop  by  drop, 
until  a  faint  blue  color  but  no  precipitate  remains  in  the 
liquid  after  shaking;  now  add  the  protein  solution.     A 
violet  color  indicates  protein;  a  pink,  peptone. 

(c)  Precipitation  Tests. — Solutions  of  the  proteins  are 
precipitated  by  the  following  reagents: 

Alcohol. 
Tannic  Acid. 
Picric  Acid. 

(d)  Coagulation  by  Heat. — Heat   some  of  the  fluid 
to  boiling  and  add,  drop  by  drop,  very  dilute  acetic  acid 
(2  per  cent.)  as  long  as  a  precipitate  forms;  note  that 
this  precipitate  does  not  appear  unless  the  solution  is 
acid.     Attempt   to    filter   some   of    albumen   through   a 
wet  filter-paper;  prove  by  one  of  the  above  tests  that 
no  protein  is  in  the  filtrate.     Repeat  the  above  test,  using 
first  undiluted  egg  albumen  and  second  a  very  dilute  so- 
lution (i  cc.  to  100  cc.  of  water). 

2.  Special  Tests  for  Albumens  and  Globulins. — (a)  Mil- 
Ion's. — To  a  small  portion  of  the  solution,  add  Millon's 


142  HOUSEHOLD    CHEMISTRY 

reagent  and  heat.  This  forms  a  white  precipitate  which 
turns  red  on  cooling,  or  gives  a  red  color  if  only  a  trace 
of  protein  is  present. 

(&)  Heller's  Test. — Place  some  strong  nitric  acid  in 
a  test-tube  and  allow  a  solution  of  albumen  to  flow  gent- 
ly down  the  sides  of  the  tube;  a  white  ring  of  precipi- 
tated albumen  forms  at  the  junction. 

(c)  Metaphosphoric  Add  Test. — Add  a  solution   of 
albumen  to  a  very  little  cold  freshly  prepared  metaphos- 
phoric  acid  and  note  the  precipitate  formed. 

(d)  Precipitation  Tests. — To  portions  of  the  solution 
in  separate  test-tubes  add: 

Acetic  acid  and  potassium  ferrocyanide. 
Mercuric  chloride. 
Lead  acetate. 

3.  Separation  Tests. — (a)  To  a  portion  of  the  solution, 
add  an  excess  of  dry  crystallized  ammonium  sulphate, 
shake  vigorously.       Albumen  and  globulin  will  be  pre- 
cipitated, without  change  in  composition. 

(b)  To  a  portion  of  the  solution,  add  dry  sodium 
chloride  or  magnesium  sulphate.  Globulin,  only  will  be 
precipitated. 

4.  Indiffusibility. — Place   some  of  the  solution   in  a 
dialyzer  of  parchment  paper  and  suspend  the  whole  in  a 
beaker  of  distilled  water.     Test  the  water  subsequently 


PROTEIN    BODIES  143 

for  chlorides  with   silver  nitrate  and   also   for  protein 
by  the  biuret  test. 

5.  Proteolysis. — (a)  Acid  Metaprotein. — To  undiluted 
egg  white  add  cone.  HC1;  note  the  copious  precipitate 
of  albumen  (coagulated).  Heat  gently  until  the  mass 
dissolves  resulting  in  a  violet  solution.  Cool  and  dilute 
some  of  this  liquid  testing  it  as  follows : 

1.  Heat  to  coagulating  point    (70°   C.). 

2.  Neutralize  with  dilute  caustic  soda. 

3.  Make  the  biuret  test. 

4.  Add  a  few  drops  to    15-20  cc.   saturated   sodium 
chloride. 

5.  Add  a  few  drops  to  15-20  cc.  95  per  cent,  alcohol. 

(b)  Alkali  Metaprotein. — Treat  undiluted  white  of 
egg  with  strong  alkali;  note  the  clear  jelly-like  mass 
which  results.  Dilute  some  of  this  with  water  and  make 
the  following  tests : 

1.  Heat  to  coagulating  point  (70°  C.). 

2.  Neutralize  with  dilute  acetic  acid. 

3.  Make  the  biuret  test. 

4.  Add  a  few  drops  to  15-20  cc.  saturated  sodium  chlo- 
ride. 

5.  Add  a  few  drops  to  15-20  cc.  of  95  per  cent,  alcohol. 

Note.  Weaker  solutions  of  albumen  are  converted 
by  treating  with  a  few  cc.  of  very  weak  alkali  or  acid 
(o.i  per  cent.)  at  100°  F.,  for  some  time. 


144  HOUSEHOLD    CHEMISTRY 

(c)  Protease  and  Peptone. — The  action  of  pepsin  is 
hydrolytic  and  produces  both  proteose  and  peptone — a 
case  similar  to  the  production  of  dextrine  and  glucose 
from  starch. 

Preparation  of  Proteose  and  Peptone. — Coagulate  egg 
albumen  by  heat.  Cut  into  small  wedge-shaped  pieces, 
put  into  three  test-tubes  and  treat  as  follows: 

1.  Cover   with    highly   dilute   hydrochloric   acid    (0.2 
per  cent.). 

2.  Add  water  and  a  very  small  amount  of  neutralized 
pepsin  solution  (o.i  per  cent.). 

3.  Add  both  pepsin  and  hydrochloric  acid. 

Place  all  three  tubes  in  a  beaker  of  cold  water,  heat 
to  body  temperature  and  note  the  time  they  take  to 
clear ;  also  observe  whether  the  mass  swells ;  finally  filter 
all  three  and  test  the  clear  filtrates  for  peptone  by  the 
biuret  test. 

GLOBULINS 

Globulin  from  the  White  of  Egg. — Saturate  some  of 
the  undiluted  solution  with  dry  magnesium  sulphate, 
grinding  the  mass  in  a  mortar.  Observe  the  precipitate 
of  globulin,  filter  and  test  the  filtrate  for  protein,  now 
pour  water  through  the  insoluble  mass  on  the  filter  and 
test  the  extract  for  proteins.  Explain.  The  yield  of 
globulins  obtained  from  this  source  is  very  small  and  the 
following  method  is  preferable. 


PROTEIN    BODIES  145 

Globulin  from  Hemp-Seed. — Extract  dry,  ground  hemp- 
seed  with  5  per  cent,  salt  solution,  heating  the  mixture 
gently  but  not  above  50°  C. ;  filter  and  test  the  clear 
filtrate  as  follows: 

1.  Heat  to  coagulating  point:  what  is  it? 

2.  Add  sodium  chloride  to  saturation,  filter  and  test 
the  precipitate  with  nitric  acid  and  with  biuret. 

3.  Make  the  biuret  test  for  protein  on  some  of  the 
saline  solution. 

YOLK  OF  EGG 

Place  one-half  the  yolk  of  a  fresh  egg  in  a  broad  six- 
inch  test-tube,  add  twice  its  bulk  of  ether,  cork  and  shake 
well :  allow  the  tube  to  rest  until  the  contents  separate 
into  layers,  uncork  the  tube  and  pour  carefully  the  up- 
per (ether)  layer  into  a  clean  porcelain  dish  and  reserve 
for  future  use.  Add  another  portion  of  ether  to  the  tube, 
cork  and  shake.  Allow  it  to  stand  until  it  has  settled, 
pour  off  the  clear  ether  solution  as  before,  adding  it  to 
the  ether  solution  obtained  by  the  first  operation.  Re- 
peat these  washings  at  least  four  times  or  until  the  resi- 
due in  the  tube  is  white  or  nearly  so.  Dry  the  residue 
over  hot  water  and  reserve  for  future  test,  it  is  princi- 
pally vitellin. 

Evaporate  the  combined  extracts  over  hot  water  (  no 
flame).  When  the  ether  has  passed  off,  note  the  yellow 
liquid  oil  similar  in  color  to  melted  butter. 


146  HOUSEHOLD    CHEMISTRY 

Put  a  drop  or  two  in  water:  notice  that  it  does  not 
mix  and  is  oily.  Now  add  two  or  three  drops  of  con- 
centrated nitric  acid  to  the  contents  of  the  dish,  and 
note  the  change  of  color.  Then  add  a  few  drops  of 
water  and  ammonium  thiocyanate;  red  color  indicates 
iron. 

Vitellin. — Make  a  soluticn  in  a  small  amount  of  10 
per  cent,  salt  solution ;  filter  and  test  as  follows : 

1.  Add  to  a  larger  bulk  of  water  faintly  acid  with 
acetic  acid. 

2.  Heat  to  75°  C. 

3.  Nitric  acid  test. 

Shell. — i.  Examine  a  portion  of  the  shell  under  the 
low  power  of  a  microscope;  note  the  physical  character. 
Treat  a  portion  of  the  shell  with  dilute  silicate  of  soda 
solution:  when  dry  examine  as  before.  (Silicate  of 
soda  is  used  for  preserving  eggs.) 

2.  Crush  and  grind  the  shell,  thoroughly  extract  with 
warm  water,  dissolve  the  extracted  mass  with  dilute  hy- 
drochloric acid.  Note  the  effervescence.  Hold  in  the 
fumes  a  drop  of  limewater  on  the  end  of  a  glass  rod 
and  note  the  clouding.  What  gas  is  formed?  Filter 
the  HC1  solution  and  make  slightly  alkaline  with  am- 
monia, add  ammonium  oxalate  and  note  the  white  pre- 
cipitate of  calcium  oxalate,  insoluble  in  acetic  acid.  From 


PROTEIN    BODIES  147 

the  data  found  give  the  composition  of  the  shell  and  the 
changes  which  have  taken  place. 

3.  Allow  an  egg  to  stand  in  strong  vinegar  for  sev- 
eral hours,  remove,  wash  in  one  change  of  water,  and 
note  the  peculiar  condition  of  the  egg.     Examine  the 
acid  liquid  as  in  the  preceding  experiment. 

4.  Examine  equal  portions  of  the  yolk  and  the  white 
of  egg,   for  sulphur  by  mixing  with  lime  and  testing 
with    the    lead    acetate    method    given    under    proteins. 
Which  do  you  think  contains  the  greater  amount  of  sul- 
phur ? 

5.  Weigh  an  egg  accurately  and  repeat  the  weighing 
for  five  or  six  succeeding  days.     Record  the  results  and 
explain. 

GELATINE 

By  prolonged  boiling  with  water  gelatine  is  produced 
from  collagen  which  is  a  protein  occurring  in  the  conec- 
tive  tissue. 

Place  small  pieces  of  gelatine  in  contact  with  cold 
water  and  note  any  change  which  takes  place,  then  slow- 
ly heat  the  mixture  to  boiling:  does  it  coagulate?  Cool 
a  portion  of  the  liquid :  what  happens  ?  Test  the  re- 
mainder of  the  warm  solution,  divided  into  seven  parts 
with: 

1.  Dilute  hydrochloric  acid. 

2.  Acetic  acid  or  lemon  juice. 

3.  Picric  acid. 


148  HOUSEHOLD    CHEMISTRY 

4.  Acetate  of  lead. 

5.  Salt  and  tannin. 

6.  Heller's  test. 

7.  Biuret  test. 

Note.  Any  response  to  Millon's  test  shows  albumen 
or  globulin  (impurities). 

COMPOSITION  OF  BONES 

Bony  tissue  consists  of  a  mixture  of  mineral  matter 
(largely  phosphate  of  lime)  with  protein  (ossein).  The 
presence  of  both  is  easily  shown  by  simple  processes.  If 
fresh  bones  be  steeped  for  several  days  in  10  per  cent, 
hydrochloric  acid,  the  mineral  matter  will  be  removed 
and  a  shrunken  but  flexible  cast  will  remain.  On  the 
other  hand,  the  mineral  matter  of  bone  will  persist  after 
long  careful  heating  in  its  original  shape.  The  same 
result  is  accomplished  much  more  slowly  by  weather- 
ing. 

Procure  raw  shin  bones  of  beef  and  have  them  well 
scraped  and  sawed  into  one  inch  sections.  Treat  these 
sections  for  two  or  three  hours,  under  slight  pressure, 
in  a  soup  digester  with  the  least  possible  amount  of 
water.  Pass  the  extract  through  cheese-cloth,  filter  into 
a  tall  glass  cylinder,  and  allow  it  to  cool  and  reserve  for 
future  use. 

Tests  on  the  extracted  bone: 


PROTEIN    BODIES  149 

1.  Dry  and  examine  the  bone,  comparing  its  condition 
before  and  after  treatment. 

2.  Break  the  extracted  bone  into  small  pieces  and  char 
a  few  of  these  in  a  small  porcelain  dish.     Note  the  dis- 
agreeable odor  of  the  fumes  evolved  in  the  operation. 
When  these  have  ceased  allow  the  mass  to  cool  somewhat 
and  then  transfer  to  a  clean  dry  test-tube  and  cork  tight- 

iy. 

Note.  This  material  is  known  as  bone-black  and  is 
largely  used  for  decolorizing  many  food  products,  not- 
ably sugar. 

3.  When  the  contents  of  the  test-tube  are  thoroughly 
cool,  pulverize  them  in  a  mortar.     Test  the  decolorizing 
power  by  placing  a  portion  of  the  bone-black  in  a  dry 
filter-paper  and  passing  diluted  molasses  through  it,  re- 
peating the  operation,  if  necessary,  and  compare  with 
the  unfiltered  portion. 

4.  Ignite  another  portion  of  the  bone-black  on  a  plati- 
num foil  until  a  white  ash  is  obtained.     Dissolve  this  ash 
in  dilute  nitric  acid  and  test  for  lime  and  phosphoric 
acid  in  the  usual  manner. 

Tests  on  the  Water  Extract: 

1.  When   thoroughly   cool,   remove  the  layer  of   fat 
and  compare  with  tallow  obtained  in  a  previous  experi- 
ment. 

2.  Make  tests  for  protein  (biuret)  and  gelatine  on  the 
balance  of  the  extract. 


150  HOUSEHOLD    CHEMISTRY 

MUSCLE 

The  muscle  mass  consists  of  a  series  of  elongated 
tubular  sacks  of  yellow  connective  tissue  (elastic)  more 
or  less  filled  with  a  mixture  of  the  proteins  myosinogen 
and  haemoglobin,  mineral  matter  and  water.  The  tubes 
are  arranged  in  bundles  held  together  by  white  connec- 
tive tissue  (collagen),  interspersed  in  the  mass  are  fat 
globules. 

While  living  muscle  contains  myosinogen  at  death  it 
is  clotted  by  enzyme  action,  the  globulin  myosin  result- 
ing. This  in  turn  is  slowly  softened  by  the  acids  set 
free  by  bacterial  action  (putrefaction)  during  "hang- 
ing." 

The  muscle  tubes  are  not  affected  by  ordinary  cooking 
processes,  while  the  white  connective  tissue  gradually 
yields  gelatine  even  at  temperature  below  boiling.  Fresh 
muscle  usually  contains  glycogen  but  on  standing  this 
is  rapidly  replaced  by  lactic  acid. 

Experiments  on  Muscle. — Cut  off  the  exterior  of  a  piece 
of  lean  meat,  test  the  interior  with  litmus  paper  and  note 
the  reaction.  Then  cut  the  meat  in  small  pieces,  pass 
through  a  meat  chopper  and  grind  the  resulting  mass  in 
a  mortar  with  clean,  dry  sand.  Take  one-half  of  the 
ground  mass  and  extract  in  a  beaker  of  cold  water, 
stirring  every  few  minutes.  Allow  the  extraction  to 
proceed  for  half  an  hour;  while  this  is  proceeding,  take 


PROTEIN    BODIES  151 

the  balance  of  the  ground  mass  and  extract  with  10  per 
cent,  salt  solution,  stirring  as  before.  Finally  pour  off 
and  filter  the  first  watery  extract  into  four  parts,  test- 
ing each  as  follows: 

1.  Biuret. 

2.  Heat. 

3.  Add  crystals  of  ammonium  sulphate  to  saturation. 

4.  Boil  with  a  few  drops  of  hydrochloric  acid,  neutra- 
lize with  caustic  potash,  add  Fehling's  solution  and  boil : 
note  the  result  (glycogen). 

Saline  solution  must  stand  at  least  one  hour  (better 
twenty-four)  ;  after  standing  pour  off  the  solution  of 
proteins  and  test  as  follows: 

1.  Pour  a   few  drops  into  a  large  excess  of  water, 
milky  deposit  of  myosin,  soluble  in  10  per  cent,  salt  so- 
lution. 

2.  Heat  short  of  boiling  and  note  the  result :  cool,  and 
test  the  liquid  with  litmus  paper. 

3.  Saturate  with  salt,  precipitate  of  myosin,  filter,  dis- 
solve precipitate  in  weak  salt  solution    (10  per  cent.), 
and  make  biuret  test. 

4.  Suspend  a  crystal  of  rock  salt  in  the  solution  and 
note  the  result. 

Make  a  water  solution  of  meat  (without  washing  out 
the  blood),  heat  to  coagulate  the  protein  and  filter.  To 


152  HOUSEHOLD    CHEMISTRY 

the  filtrate,  add  a  few  drops  of  concentrated  HNO3; 
evaporate  the  liquid  to  dryness  and  ignite.  Cool  and 
take  up  with  water;  if  cloudy,  filter.  Divide  into  five 
parts  and  test  as  follows: 

1.  For  chlorides  with  nitric  acid  and  silver  nitrate. 

2.  For  sulphates  with  hydrochloric  acid  and  barium 
chloride. 

3.  For   phosphates   with   nitric  acid   and   ammonium 
molybdate. 

4.  For  calcium  with  ammonium  hydroxide   and  am- 
monium oxalate. 

5.  For   iron   with  hydrochloric   acid   and   ammonium 
thiocyanate. 

Tests  on  Homemade  and  Commercial  Extracts: 
Make  meat  extract  by  steeping  lean  meat  in  cold  salt 
water,  gradually  heating  to  a  boil  and  finally  under  slight 
pressure.  Pour  off  the  liquid,  cool,  remove  the  fat,  dis- 
solve some  of  the  jelly  in  warm  water  and  compare  with 
Liebig's  and  other  meat  extracts  made  on  the  commercial 
scale,  by  the  following  tests: 

1.  Biuret. 

2.  Glycogen  test  (Iodine). 

3.  Creatinin,  Weyl's  test:   add  a  very  dilute   freshly 
prepared  solution  of  sodium  nitroprusside  and  cautiously 
caustic  soda — ruby-red  changing  to  straw  color. 

4.  Examine  the  solid  extract  under  the  microscope  and 


PROTEIN    BODIES  153 

note  the  cubical  crystals  of  salt  and  knife-rest  forms  of 
creatin. 

5.  Clarify  beef  extract  with  white  of  egg,  filter  and 
test  filtrate  for  protein  with  Biuret  test.  Compare  with 
test  on  beef  extract  before  clarifying. 


Chapter  XIII 


MILK 

This  term  usually  expresses  cow's  milk  in  market 
condition.  Experience  has  shown  that  this  is  a  liquid 
consisting  of  87  per  cent,  of  water  and  13  per  cent,  of 
solids  of  which  3  per  cent,  is  fat  and  in  consequence  this 
composition  is  now  required  by  law.  The  three  per  cent, 
of  fat,  technically  known  as  butter-fat,  is  not  in  solution 
but  in  suspension  and  separates  almost  entirely  mixed 
with  more  or  less  of  the  soluble  solids,  on  standing  and 
is  called  cream.  The  balance  of  the  solution  is  known  as 
skim  milk. 

The  following  gives  a  fair  idea  of  the  more  important 
ingredients  and  their  quantities: 

Water 87.00 

Fats 3.00 

Protein 4.30 

Sugar 5.00 

Salts : 0.70 


The  fats  in  suspension  are  in  the  form  of  minute 
globules  (emulsion)  coated  with  the  soluble  constituents 
and  will  not  run  together  in  mass  until  the  coatings  are 
removed  by  the  action  of  acids  (lactic)  produced  by 


MILK  155 

bacterial  development  some  heat  and  mechanical  agita- 
tion (churning).  The  protein  matter  consists  largely 
of  caseinogen,  with  smaller  amounts  of  albumen  and 
globulin.  All  milk  sours,  i.e.,  becomes  acid  due  to  for- 
mation of  lactic  acid  at  the  expense  of  some  of  its  lac- 
tose. 

Cl2Km0lu  H20   =   4C3H6O3. 

When  the  amount  of  lactic  acid  reaches  approximately 
0.5  per  cent.,  the  caseinogen  precipitates  without  change 
of  composition  (curdles).  On  neutralizing  with  alkali, 
it  goes  back  into  solution.  As  milk  is  a  saturated  solu- 
tion of  its  constituents,  any  removal  of  water  usually 
by  means  of  heat,  produces  a  precipitate  which  makes  its 
appearance  on  the  surface  in  the  form  of  a  skin.  Break 
this  and  another  forms  and  so  in  like  manner  until  no 
more  liquid  is  left.  No  coagulation  takes  place  except 
in  the  case  of  the  very  small  amount  (0.5  per  cent.)  of 
albumen  present. 

The  mineral  matter  consists  very  largely  of  phosphates 
of  lime,  whose  peculiar  function  in  keeping  the  casein- 
ogen in  solution  is  well  known.  Soluble  citrates  of  lime 
and  magnesium  are  also  present  in  considerable  quanti- 
ties, together  with  the  chlorides  of  potassium  and  sod- 
ium. 

Fresh  milk  reacts  acid  and  alkaline  to  delicate  litmus 
paper,  due  to  presence  of  acid  and  alkaline  reacting  phos- 


156  HOUSEHOLD    CHEMISTRY 

phates.     Old  milk  is  always  acid.     Specific  gravity  of 
milk  varies  from  1.028-1.033. 

TESTS 

Physical. — i.  Cream  Gauge. — Fill  to  mark  with  fresh- 
ly mixed  milk.  Allow  the  tube  and  contents  to  rest 
quietly  for  half  an  hour  and  read  off  percentage  of  top 
milk  from  graduated  scale. 

2.  Lactometer. — Fill    a   tall    jar   with    freshly   mixed 
milk,  temperature  6o°-7o°  F.     Immerse  the  instrument 
and  when  it  comes  to  rest  read  off  the  percentage  of 
purity  on  the  scale.     In  similar  manner,  determine  the 
purity  of  skim  milk.     Finally,  add  water  and  redeter- 
mine  the  purity;  how  can  you  explain  the  result. 

3.  Pio scope  Test. — Depends  on  opacity.     Place  a  drop 
or  two  of  freshly  mixed  milk  in  the  center  of  the  hard 
rubber  disc.     Cover  carefully  with  the  glass  plate  and 
compare  with  the  standard  scale  of  colors. 

4.  Lactoscope  Test. — Use  Feser's  lactoscope.     Fill  the 
pipette  with  milk,   allow   it  to   run   into   the   cylinder. 
Cautiously  add  water,  shaking  after  each  addition,  until 
the  marks  on  the  cloudy  glass  rod  are  just  visible  through 
the  liquid,  read  off  and  record  the  percentage  of  fat  at 
the  level  of  the  liquid. 

5.  Microscope  Test. — Examine  a  drop  of  milk  under 
the  microscope :  add  a  drop  of  10  per  cent,  caustic  soda 
and  re-examine.    What  is  the  result. 


MILK         -  157 

Chemical  Tests. — i.  Using  fresh  milk,  what  is  the  re- 
action with  delicate  litmus  paper? 

2.  Babcock  Test  (Determination  of  Fat}. — This  test 
depends  on  the  decomposition  of  the  organic  constitu- 
ents, with  the  exception  of  the  fats,  which  are  at  the 
same  time  set  free  in  the  liquid  state  and  may  be  meas- 
ured. 

Fill  the  milk  pipette  (17.6  cc.)  with  freshly  mixed 
milk  discharging  the  contents  into  the  Babcock  bottle, 
add  an  equal  volume  of  oil  of  vitriol  (sp.  gr.  1.8).  Mix 
by  revolving  the  bottle  gently  in  a  small  arc,  back  and 
forth,  until  the  residue  disappears  and  the  mass  is  brown 
in  color.  Make  tests  up  in  duplicate  and  whirl  them 
for  5  minutes  in  the  centrifuge  over  hot  water.  Stop 
the  machine,  add  enough  warm  water  to  bring  liquid  level 
half  way  up  the  graduated  neck  of  bottle.  Replace  them 
in  centrifuge  and  whirl  three  minutes,  allowing  machine 
to  run  down.  Take  out  bottle  and  read  per  cent,  of 
clear  yellow  fat  floating  on  the  water. 

3.  Separation  and  Identification  of  Caseinogen. — Dilute 
some  milk  with  10  volumes  of  water  and  carefully  neu- 
tralize with  dilute  acetic  or  hydrochloric  acid;  no  pre- 
cipitate appears;  why?    Cautiously  add  more  acid  until 
there  is  a  copious  precipitate  (caseinogen).     This  action 
is  hastened  by  heating  to  70°  C.     Filter  through  a  moist 
fluted  paper  and  wash  well.     Reserve  the  clear  filtrate 
for  test  B. 


158  HOUSEHOLD    CHEMISTRY 

A.  Residue  of  Caseinogen. — Treat  residue  on  the  filter- 
paper  with  a  moderate  amount  of  warm  10  per  cent,  salt 
solution  pouring  it  through  the  filter  several  times.  Add 
some  of  this  liquid  carefully  to  a  saturated  solution  of 
salt,  adding  dry  salt  if  necessary.     Observe  the  precipi- 
tate (caseinogen)  which  dissolves  on  addition  of  water. 

B.  Divide  the  filtrate  (reserved)  into  three  equal  posi- 
tions. 

1.  Heat    to   7o°-75°    C.    and    observe    the    clouding 
(lactalbumen).     Filter,  test  precipitate  by  biuret  and  fil- 
trate for  lactose  with  Fehling's  reagent. 

2.  Add  potassium  ferrocyanide  and  excess  of  acetic 
acid.     Observe  the   precipitate  of  lactalbumen. 

3.  Heat  to  70°-75°  C.  filter  off  lactalbumen,  boil  the 
filtrate  and  observe  the  precipitate  of  insoluble  calcium 
citrate.     Reserve  filtrate. 

Note. — If  milk  has  been  thoroughly  pasteurized,  it  will 
not  respond  to  the  tests  for  lactalbumen. 

C.  Evaporate  the  filtrate,  from  last  test,  to  dryness; 
ignite  in  the  presence  of  a  few  drops  of  HNO3,  cool  di- 
lute with  water  and  test   for  chlorides,  sulphates   and 
phosphates. 

Quantitative  Analysis  of  Milk. — Measure  5  cc.  of  milk 
with  a  pipette,  transfer  it  to  a  weighed  shallow  por- 
celain dish  and  weigh  again.  Difference  is  weight  of 
milk.  Place  over  hot  water  (kept  just  below  the  boiling- 


MILK  159 

point)  to  evaporate  water  present  in  milk.  Cool  and 
weigh ;  loss  is  water,  residue  is  total  solids.  Total  solids 
should  be  12-13  per  cent.  To  extract  fat,  add  about  10 
cc.  of  ether  to  contents  of  dish,  heat  over  warm  water 
one  or  two  minutes,  decant  solution  into  a  second  weighed 
dish.  Repeat  the  ether  treatment  three  times.  When 
dry,  \veigh  original  dish ;  the  loss  is  fat.  Evaporate 
ether  from  second  dish,  weigh ;  the  gain  is  fat  and  should 
check  the  loss. 

To  extract  lactose  and  soluble  salts,  treat  contents  of 
dish  with  warm  water.  Allow  it  to  stand  for  several 
minutes,  decant  the  liquid;  repeat  the  operation  three 
times.  Dry  the  dish  and  weigh;  loss  is  lactose  and  half 
the  mineral  salts  found  in  milk. 

Protein  and  Insoluble  Salts. — Ignite  the  contents  of 
dish  to  a  gray  ash ;  protein  matter  will  burn  off.  Cool 
and  weigh;  the  loss  is  protein,  residue  is  insoluble  salts. 
Assuming  that  insoluble  salts  are  one-half  of  the  total 
salts,  double  the  figure  obtained.  To  determine  amount 
of  lactose,  subtract  one-half  of  total  salts  from  the  figure 
obtained  on  lactose  and  soluble  salts.  The  difference 
is  the  amount  of  lactose. 

Determination  of  lactose  Quantitatively. — Into  a  glass 
stoppered  cylinder,  put  100  cc.  milk  and  2  cc.  Millon's 
reagent.  Mix  thoroughly  and  pour  into  a  beaker  placed 
over  hot  water.  Allow  the  mixture  to  stand  until  all 


l6o  HOUSEHOLD    CHEMISTRY 

protein  matter  has  precipitated,  filter  off  the  clear  whey 
through  moist  fluted  paper.  Make  it  alkaline  with  dry 
sodium  carbonate,  adding  a  little  at  a  time  until  pink  lit- 
mus paper  turns  blue.  If  cloudy  filter  again.  Pour  into 
a  burette  and  deal  with  it  as  with  sugar.  Calculate  that 
0.068  gram  will  reduce  10  cc.  Fehling's  reagent. 

Effect  of  Rennet. — i.  Heat  one  cup  of  milk  to  the  boil- 
ing-point, boil  gently  for  five  minutes,  cool  to  40°  C.  and 
add  rennet;  note  the  character  and  amount  of  clot. 

2.  Boil  one  cup  of  milk  15-20  minutes,  replacing  any 
liquid  lost  during  evaporation  by  hot  distilled  water ;  cool 
to  40°  C.,  add  rennet,  note  character  and  amount  of 
clot. 

3.  To  one  cup  of  milk,  add  1-2  cc.  of  ammonium  oxa- 
late  solution  (precipitant  for  lime)  boil  for  2-3  minutes, 
cool   to  40°    C.    and   add    rennet;   note   character   and 
amount  of  clot,  if  any.     Finally  add  limewater  equal  in 
bulk  to  the  original  milk,  warm  to  40°  C.  and  note  the  re- 
sult. 

4.  Note  the  effect  of  rennet  on  separate  portions  of 
milk  heated  to  30°,  40°,  50°,  80°  C.     Tabulate  the  re- 
sults of  the  above  tests. 

Butter-Fats.— Half  fill  two  6  in.  test-tubes,  one  with 
whole  milk  and  the  other  with  skim  milk.  Add  to  each 
half  a  volume  of  ether  and  a  few  drops  of  caustic  soda, 
cork  and  shake  well.  Uncork  and  place  in  a  beaker  of 


161 


warm  water  and  allow  it  to  remain  quiet.  In  a  few 
minutes,  note  the  layer  of  oil  and  ether  floating  on  the 
surface.  Remove  some  of  the  ether  layer  from  each 
with  a  pipette  and  evaporate  at  a  low  heat.  Note  the 
difference  in  amount  of  the  butter  residue. 

Souring.  —  Place  some  milk  in  a  wide-mouthed  bottle, 
allow  it  to  stand  in  a  warm  place  for  some  days  or 
until  sour.  Finally  filter  off  the  curd  and  test  the  filtrate 
for  lactose  and  for  acidity  by  titrating  with  lo/N  alkali, 
calculating  to  lactic  acid.  What  weight  of  bi-carbonate 
of  soda  would  neutralize  the  amount  of  acid  found? 

Condensed  or  evaporated  milks  should  be  diluted  with 
distilled  water  to  the  original  bulk  and  treated  as  nor- 
mal milks. 

Preserved  milks  commonly  contain  cane-sugar.  Di- 
lute a  sample  to  the  original  bulk,  precipitate  the  casein- 
ogen  with  dilute  acetic  acid;  filter  and  exactly  neutralize 
the  filtrate  with  sodium  carbonate  and  test  for  sucrose 
with  cobalt  chloride  and  caustic  soda. 

The  presence  of  formalin  in  milk  will  be  noticed  in  the 
Babcock  test,  by  the  appearance  of  a  violet  band  at  the 
junction  of  the  acid  and  oily  layers. 

Borax  and  borates  will  be  found  with  the  ash. 


A  product  prepared  from  the  caseinogen  of  milk  with 
or  without  the  fat.    The  milk  is  clotted  with  rennet,  sep- 


l62  HOUSEHOLD    CHEMISTRY 

arated  from  the  whey,  ground,  salted,  pressed  into  shape 
and  cured.  The  curing  operation  consists  in  subjecting 
the  cheese  mass  to  the  action  of  certain  bacteria  and 
moulds,  which  form  acids,  hydrolyze  the  proteins  and 
develop  flavor  and  odor. 

Cottage  cheese  is  merely  finely  divided  caseinogen  pre- 
cipitated by  the  lactic  acid  of  the  souring  process  and 
undergoes  no  further  change. 

Cheeses  are  usually  made  from  cow's  milk  but  may  be 
produced  from  goat's  or  ewe's  milk  or  mixtures  of  all 
of  them. 

EXPERIMENTS  ON  CHEESE 

Take  a  sample  of  any  well-cured  cheese,  grind  some  of 
it  in  warm  water,  filter  and  reserve  the  residue. 

Divide  the  filtrate  into  six  parts  and  test  as  follows: 

1.  For  acidity  or  alkalinity  with  litmus  paper  and  N/io 
acid  or  alkali. 

2.  For  soluble  protein. 

3.  Neutralize  for  meta-protein. 

4.  For  peptone. 

5.  For  soluble  mineral  matter,  i.e.,  chlorides,  sulphates, 
etc. 

6.  For  ammonia  and   sulphides. 

Extract  the  residue  several  times  with  the  same  por- 
tion of  warm  neutral  alcohol  and  test  the  extract  for 
fatty  acids.  Again  extract  the  residue  with  warm  ether 


MILK  163 

several  times  and  evaporate  some  of  the  clear  ethereal 
liquid  over  warm  water.     Is  the  residue  greasy? 

Divide  the  extracted  residue  into  two  parts  and  test 
as  follows: 

1.  For  insoluble  protein. 

2.  Burn  to  white  ash  and  test  for  insoluble  mineral 
matter, — phosphates,  lime,  etc. 

During  the  incineration,  hold  pieces  of  moistened  red 
litmus  and  lead  acetate  papers  in  the  fumes  and  record 
the  results. 

Cheeses  are  frequently  preserved  in  wrappings  satur- 
ated with  borax  or  boracic  acid  solution.  To  determine 
this,  steep  some  of  the  paper  wrapping  in  warm  water 
filter  if  necessary,  acidify  with  HC1  and  dip  pieces  of 
turmeric  paper  in  the  liquid.  Dry  these  at  212°  F.,  a 
pink  color  indicates  borates. 


Chapter  XIV 


FERMENTS  AND  PRESERVATIVES 

The  organisms  which  cause  the  most  common  changes 
in  our  food  materials  are  generally  known  as  yeasts, 
lactic  acid  and  vinegar  ferments.  Their  spores  are 
present  in  all  house  dust.  These  organisms  are  dis- 
tinguished by  the  fact  that  they  operate  in  presence  of  air, 
under  widely  varying  temperature  conditions,  and  give 
off  no  disagreeable  odors  while  their  products  are  non- 
poisonous.  It  is  true  that  putrefactive  bacteria  play  some 
part  in  the  preparation  of  our  food,  notably  in  meats  and 
cheeses,  but  great  care  must  be  observed  that  the  pro- 
cess is  kept  under  strict  control  and  only  allowed  to 
proceed  to  a  limited  extent.  Yeasts  so  familiar  as  pro- 
ducers of  fermentation,  work  on  starch,  maltose,  sugar 
and  the  glucoses.  At  least  two  enzymes  are  secreted  by 
these  organisms,  i.e.,  invertase,  changing  starch,  maltose 
and  sugar  into  glucose;  and  zymase,  changing  the  glu- 
cose into  carbon  dioxide  and  alcohol.  These  changes 
occur  between  32°  and  I22°F.,  and  are  at  a  maximum 
at  92°  F.  When  15  per  cent,  of  alcohol  has  been  formed 
even  if  the  material  contains  unchanged  carbohydrate, 
the  action  ceases.  Yeasts  are  not  easily  destroyed  by 
cold  unless  exposed  to  very  low  temperatures  for  long 
periods.  Above  122°  F.,  however,  they  are  quickly 


FERMENTS  AND  PRESERVATIVES  165 

killed  so  that  it  is  not  necessary  to  reach  the  boiling 
point  212°  F.  (sterilization).  If  a  lower  temperature  be 
employed,  it  is  well  to  maintain  it  for  some  time  to  insure 
uniform  heating  of  the  mass  (pasteurization).  Varieties 
of  yeasts  are  known  as  Brewer's  Distiller's  and  Wild. 
Lactic  acid  bacteria  chiefly  attack  the  sugar  of  milk, 
working  until  about  one  per  cent,  of  acid  is  formed,  but 
always  leaving  much  of  the  carbohydrate  unchanged. 
They  are  not  easily  destroyed  by  cold  but  do  not  act 
below  50°  F.  and  continue  their  work  up  to  130°  F.,  be- 
ing most  active  at  110°  F.  Conditions  for  sterilization 
and  pasteurization  are  similar  to  yeasts.  The  other  car- 
bohydrates are  less  susceptible  to  this  ferment;  sour 
bread  and  sauerkraut,  however,  are  the  result  of  their 
work. 

Acetic  or  vinegar  ferments  act  on  all  weak  alcoholic 
liquids;  10  per  cent,  and  under.  The  temperature 
conditions  are  much  the  same  as  for  lactic  acid  (50°- 
110°  F.).  Fermentation  ceases  when  5  per  cent,  of  acid 
has  been  produced.  The  ferment  is  commonly  known 
as  "Mother  of  Vinegar."  Conditions  for  sterilization  and 
pasteurization  are  similar  to  yeasts. 

Yeast — Temperature  Experiments. — Prepare  four  six- 
inch  test-tubes  with  perforated  corks,  bearing  tubes  bent 
in  the  form  of  an  inverted  letter  J.  Fill  three  of  the 
tubes  with  a  mixture,  prepared  from  one-half  a  yeast 


l66  HOUSEHOLD    CHEMISTRY 

cake,  one-half  tablespoonful  of  molasses  and  a  cup  of 
water.  Fill  the  fourth  with  the  same  preparation  filtered 
through  absorbent  cotton.  Allow  tubes  Nos.  I  and  4 
to  stand,  while  No.  2  is  subjected  to  a  temperature  of 
32°  F.  (produced  by  a  mixture  of  pulverized  ice  and 
salt)  for  fifteen  minutes.  No.  3  is  boiled  for  two  or 
three  minutes.  Now  place  the  four  pieces  of  apparatus 
so  that  the  delivery  tube  of  each  reaches  to  the  bottom 
of  a  test-tube  containing  about  two  inches  of  clear  lime- 
water,  and  allow  them  to  stand  for  at  least  twelve  hours 
in  a  warm  place  (90°  F.).  At  the  end  of  this  time  examine 
each  tube  of  limewater,  first  for  a  precipitate,  and  second 
with  litmus  paper.  Finally  examine  the  liquid  in  the  fer- 
mentation tubes,  noting  its  odor  and  general  properties. 
Action  of  Yeast  on  Various  Foods. — Prepare  two  solu- 
tions of  sugar  in  water  as  follows:  For  the  first  use 
equal  quantities  of  granulated  sugar  and  water,  for  the 
second  take  one-fourth  of  the  strong  solution  and  dilute 
with  three  volumes  of  water.  Fill  two  of  the  fermenta- 
tion tubes  already  prepared  with  two  sugar  solutions 
(Nos.  i  and  2).  Dissolve  one-eighth  of  a  yeast  cake  in 
about  30  cc.  of  milk  and  pour  the  mixture  into  a  fer- 
mentation tube  (No.  3).  Fill  a  fourth  fermentation 
tube  (No.  4)  with  a  mixture  of  one-eighth  of  a  yeast  cake 
dissolved  in  thin,  clear  flour  paste.  Connect  all  four 
of  the  fermentation  tubes  with  limewater  tubes  as  be- 
fore and  allow  them  to  stand  for  twelve  hours  in  a  warm 


FERMENTS  AND  PRESERVATIVES  167 

place  (90°  F.).     Finally  examine  the  contents  of  each 
limewater  and  fermentation  tube. 

Acetous  Fermentation. — Make  a  weak  solution  of  alco- 
hol in  water  (5  parts  of  alcohol  to  20  parts  of  water) 
and  test  with  litmus  paper;  if  acid,  neutralize  with  a 
weak  solution  of  sodium  carbonate  and  test  a  small  por- 
tion with  potassium  iodide  and  potassium  hydroxide,  heat 
— the  odor  of  iodoform  shows  the  presence  of  alcohol. 

Divide  the  balance  of  the  solution  into  two  equal 
parts,  pour  one  into  a  shallow  dish  and  place  the  other 
in  a  well-corked  bottle.  After  the  solutions  have  stood 
for  a  week,  test  with  litmus  paper,  and  also  by  adding 
alcohol  and  warming  gently.  Note  the  peculiar  odor 
(ethyl  acetate — odor  of  hard  cider)  in  the  first  case  but 
not  in  the  latter.  Explain. 

Expose  a  small  quantity  of  beer  to  the  atmosphere 
for  several  days ;  subsequently  examine  for  acidity  with 
test  paper  and  for  acetic  acid  with  alcohol.  From  the 
results  of  these  experiments  explain  why  bottled  weak 
alcoholic  beverages  keep  sweet. 

Lactic  Acid. — To  about  six  ounces  of  cold  pasteurized 
milk  contained  in  a  small  flask,  add  one  tablespoonful 
of  the  liquid  obtained  by  dissolving  one  lactobacilline 
(Metchnikoff)  tablet  in  half  a  cup  of  tepid  water.  Mix 
well  and  keep  at  100°  F.  for  several  hours.  Carefully 
observe  all  changes  taking  place  and  compare  with  the 
well  known  buttermilk. 


l68  HOUSEHOLD    CHEMISTRY 

FOOD  PRESERVATION  AND  PRESERVATIVES 

All  foods  are  subject  to  the  attack  of  bacteria  and  in 
consequence  their  value  is  very  generally  seriously  im- 
paired. Methods  for  prevention  of  these  changes  have 
been  used  from  the  earliest  times  and  are  known  as 
preservation. 

At  least  two  general  types  of  process  are  in  common 
use,  viz.,  physical  and  chemical.  To  the  first  class  be- 
long such  methods  as  drying,  cooling,  and  canning.  These 
processes  are  applicable  to  all  kinds  of  foods,  possess 
high  efficiency  and  make  very  slight  changes  in  flavor, 
appearance  and  composition.  Unfortunately,  food  ma- 
terials preserved  in  any  of  these  ways  will  change  very 
rapidly  with  slight  variation  of  physical  conditions,  hence 
the  effects  are  not  permanent.  The  second  class  involve 
such  change  of  chemical  conditions  that  no  matter  what 
physical  changes  may  occur,  decomposition  cannot  taka 
place.  The  results  are  permanent  but  are  accomplished 
at  the  expense  of  flavor,  appearance,  etc. 

So  general  has  the  use  of  chemical  preservatives,  be- 
come that  a  brief  discussion  of  the  subject  seems  nec- 
essary. The  best  known  and  as  generally  conceded 
harmless  are:  alcohol,  vinegar,  sugar  and  salt  (NaCl). 
With  the  exception  of  vinegar  (acids  generally  being 
inimical  to  bacteria)  the  action  seems  to  depend  on  mak- 
ing the  protein  matter  present,  insoluble ;  hence  we  find 


FERMENTS  AND  PRESERVATIVES  169 

the  quantity  of  the  preservative  important.    Well  known 
operations  are  as  follows : 

Alcohol — 50  per  cent.  "Brandy ing." 
Salt — dry  or  supersaturated  solution  'Tickle." 
Sugar — syrup— solutions  of  25  per  cent,  or  more. 
Less  well  known  methods  accomplish  similar  results 
by  using  very  small,  in  some  cases  minute  proportions, 
of  other  chemical  agents ;  but  the  actual  chemical  opera- 
tion can  only  be  surmised  in  most  cases.    Included  in  this 
list  are:  borates,  fluorides,  sulphites,  formaldehyde,  ben- 
zoates,  salicylates  and  creosote.     It  may  be  as  well  to  ob- 
serve that  the  use  of  spices,  for  instance  in  mince  meat, 
is  certainly  parallel  with  benzoates  and  salicylates. 

EXPERIMENTS 

Alcohol  and  vinegar  are  first  separated  by  distillation 
and  then  identified  by  well  known  methods.  Sugar  and 
salt  may  also  be  determined  by  diluting,  filtering  and 
testing  the  clear  filtrate. 

Borates. — Ash  some  of  the  substance,  cool,  make  strong 
water  extract,  filter  if  necessary  and  neutralize  with  di- 
lute HC1.  Dip  a  strip  of  turmeric  paper  in  this  liquid, 
remove  and  dry  by  steam  heat.  (This  may  be  accon> 
plished  by  wrapping  the  moist  paper  around  the  upper 
part  of  a  test-tube  partly  filled  with  water  and  boiling 
gently.)  The  paper  turns  pink  on  the  edges. 


I7O  HOUSEHOLD    CHEMISTRY 

Or  moisten  the  ash  in  the  dish  with  alcohol,  add  8 
to  10  drops  of  glycerine,  mix  well  with  a  glass  rod  and 
ignite  the  mass  with  a  match  or  Bunsen  burner.  Mote 
the  yellow  flame  with  a  green  edge,  characteristic  of 
borates. 

Fluorides. — Mix  the  liquid  or  solid  mass  with  an  ex- 
cess of  limewater,  evaporate  to  dryness,  ignite,  cool  and 
make  the  etching  test. 

Sulphites. — If  present  in  quantity,  they  are  distinguish- 
ed by  their  odor  and  taste  "sulphur  match"  especially  on 
warming. 

For  small  amounts  of  sulphides,  mix  with  bromine 
water,  boil  off  excess  and  test  for  sulphates. 

Formaldehyde. — Cone.  H,SO4,  in  the  presence  of  fer- 
ric salt,  produces  a  violet  color.  (Oil  of  vitriol  contains 
enough  ferric  salt  to  act  as  a  satisfactory  reagent.) 

Benzoates. — Carefully  mix  liquid  substance  with  one- 
tenth  of  its  volume  of  chloroform  and  a  few  drops  of 
oil  of  vitriol.  Avoid  violent  shaking  (mix  with  a  circu- 
lar motion).  Allow  the  mixture  to  remain  quiet  until 
chloroform  layer  separates  out.  Remove  some  of  this 
layer  with  a  pipette  and  evaporate  it  in  a  clean  por- 
celain dish  over  hot  H2O.  Note  the  flat  crystalline  plates 
of  benzoic  acid,  which  give  off  a  pungent  odor  on  heat- 
ing. Examine  the  original  mixture  in  the  flask,  note  any 


FERMENTS  AND  PRESERVATIVES  171 

violet  color  between  layers  of  acid  liquid  and  chloroform. 
This  indicates  salicylic  acid. 

Both  benzoic  and  salicylic  acids  are  not  present  in  the 
same  liquid. 


Chapter  XV 


BAKING  POWDERS 

It  is  frequently  necessary  to  develop  carbon  dioxide 
for  leavening  purposes  more  rapidly  than  by  the  agency 
of  yeast.  For  this  purpose  the  purely  chemical  method 
by  the  acid  decomposition  of  carbonates  or  bicarbonates 
is  most  available. 

Undoubtedly  the  time-honored  custom  of  using  salera- 
tus  (bicarbonate  of  potash)  and  sour  milk  (lactic  acid) 
furnished  the  original  ideas  on  which  the  modern  mix- 
tures were  built  up. 

This  original  idea  still  survives  to  some  extent  in 
modern  practice,  but  is  open  to  at  least  two  strong  ob- 
jections. First;  that  bicarbonate  of  potash  is  no  longer 
a  commercial  article  but  is  replaced  by  the  cheaper  and 
stronger  bicarbonate  of  soda ;  still  no  change  is  made 
in  the  proportions  used.  The  quantity  should  be  reduced 
nearly  one-sixth. 

Second ;  that  it  is  very  difficult  to  estimate  the  amount 
of  lactic  acid  in  sour  milk  by  simple  means  with  any  ac- 
curacy. In  fact  the  quantity  is  usually  largely  over- 
estimated. When  milk  shows  decided  indications  of  the 
sour  stage  only  four-tenths  of  one  per  cent,  of  lactic  acid 
are  usually  found. 


BAKING  POWDERS  173 

It  must  be  remembered  that  any  excess  of  the  bicar- 
bonate used,  is  changed  into  alkaline  normal  carbonate 
by  the  heat  of  baking. 

For  the  above  stated  reasons  it  can  easily  be  seen  that 
accurately  compounded  mixtures  (leaving  neither  alka- 
line nor  acid  residues)  and  retaining  their  qualities  for 
some  time  in  the  dry  state,  but  ready  to  develop  gas  on 
addition  of  water  have  a  decided  advantage. 

In  order  to  preserve  these  mixtures  in  a  dry  state,  it 
has  been  found  advisable  to  add  to  them  such  agents  as 
raw  starch  and  pulverized  lactose  which  are  perfectly 
harmless,  and  dry  alum  which  is  deleterious,  such  addi- 
tions should  not  in  any  case  exceed  25  per  cent,  of  the 
whole  mass.  When  used  for  this  purpose  the  compounds 
are  known  as  "fillers." 

Modern  baking  powders  may  be  classed  as  tartrate, 
phosphate,  and  alum  phosphate.  All  contain  bicarbonate 
of  soda,  while  the  acting  acid  ingredient  varies,  as  fol- 
lows : 

Tartrate — Cream  of  tartar,  KHC4H4O6,  and  sometimes 
a  small  amount  of  free  tartaric  acid,  H2C4H4O6. 

Phosphate — Soluble  phosphate  of  lime,  CaH4(PO4)2. 

Alum  phosphate,  same  as  above  with  addition  of  dry 
alum  K2,  Na2,  or  (NH4)2.  A12(SO4)4. 

The  following  reactions  clearly  show  the  changes  tak- 
ing place  in  using  these  mixtures. 


174  HOUSEHOLD    CHEMISTRY 

For  tartrates : 
KHC4H4O,+NaHCO8=KNaC4H4O9+COB+H2O. 

188  84  210  44  18 

For  phosphates: 
CaH4(PO4)2+2NaHCO3=CaHPO4+ 

234  168  136 

Na2HPO4+2CO2+2H2O. 

142  88  36 

For  alum  phosphates: 
(NH4)2Al2(SO4)4+CaH4(P04)2+4NaHCO= 

475  234  336 

Al2(P04)2+CaS04+(NH4)2SO4+ 
245  136  132 

2Na2SO4+4CO2-f4H2O. 

284  176          72 

It  is  significant  that  the  tartrate  powders  leave  no  in- 
soluble residue  except  starch,  while  the  others  leave  near- 
ly one-third  of  their  weight  in  insoluble  mineral  matter 
besides  the  starch.  The  phosphates  yielding  the  acid  solu- 
ble phosphate  of  lime  of  doubtful  utility,  and  the  alum 
powders,  alumina  phosphate  and  calcium  sulphate  which 
are  positively  detrimental. 

EXPERIMENTS 

Tartrates. — Mixtures  of  cream  of  tartar  and  bicarbo- 
nate of  soda  with  starch  or  lactose  filler.  Treat  a  small 
portion  of  the  powder  with  water  and  after  the  efferves- 
cence has  ceased  test  a  portion  of  the  liquid  for  starch 


BAKING    POWDERS  175 

with  iodine  solution  and  for  lactose  with  Fehling's  solu- 
tion, boil  the  remainder  of  the  liquid,  cool,  filter  through 
fluted  paper,  and  test  with  litmus  paper. 

1.  Place  a  few  drops  of  the  clear  liquid  on  a  slide  and 
allow  it  to  evaporate  spontaneously.    Examine  the  cleft 
rectangular  crystals  of  Rochelle  salt. 

2.  Test  another  portion  of  the  solution  by  adding  one 
drop  of  fresh  cold  solution  of  ferrous  sulphate,  one  or 
two  drops  of  peroxide  of  hydrogen  and  a  large  excess  of 
caustic  potash — a  violet  color  due  to  tartrates.     Evapo- 
rate the  balance  of  the  solution  in  a  porcelain  dish,  char 
and  gently  ignite  the  residue.     Note  the  odor  while  car- 
bonizing, what  does  it  suggest?  Cool,  add  water  and  test 
with  litmus  paper:  why  is  it  alkaline? 

Neutral  tartrates  will  yield  to  the  silver  mirror  test. 

Tartrate  powders  may  contain  a  small  amount  of  bi- 
carbonate of  ammonia.  To  test  for  this,  heat  a  portion 
of  the  powder  in  a  test-tube  with  caustic  potash  solu- 
tion ;  observe  the  odor ;  or  hold  a  strip  of  moistened  red 
litmus  paper  over  the  mouth  of  the  tube. 

Phosphate  Powders. — Calcium  hydrogen  phosphate,  bi- 
carbonate of  soda  and  starch  filler.  Make  a  water  so- 
lution and  test  for  filler  as  in  the  case  of  tartrates. 
Divide  the  remainder  of  the  solution  into  three  parts. 

i.  Make  acid  with  nitric  acid,  add  a  few  cc.  to  am- 
monium molybdate  and  warm — yellow  precipitate  indi- 
cates phosphates. 


176  HOUSEHOLD    CHEMISTRY 

2.  Add  ammonium  oxalate,  and  ammonium  hydroxide 
until  alkaline  and  boil — white  precipitate  indicates  cal- 
cium.   This  should  give  a  yellowish  red  flame  on  plati- 
num wire. 

3.  As  these  powders  frequently  contain  alum  it  is  nec- 
essary to  make  a  test.    A  portion  of  the  solution  placed 
on  a  slide  and  allowed  to  evaporate  spontaneously  will 
yield  large  truncated  octahedra  of  alum.     Probably  the 
best  method  for  the  determination  of  alum  is  to  add  a 
portion  of  the  solution  to  tincture  of  logwood  diluted 
with  two  or  three  volumes  of  water,  finally  adding  an 
equal  volume  of  ammonium  carbonate.     In  the  presence 
of  alum  the  liquid  is  colored  lavender  or  dark  blue. 

Carbon  Dioxide  Determination  by  the  Scheibler  Ap- 
paratus.— Weigh  out  500  mg.  of  the  baking  powder, 
place  in  the  glass-stoppered  bottle  belonging  to  the  ap- 
paratus. Put  a  small  quantity  of  water  in  the  gutta 
percha  tube  (two-thirds  full).  The  columns  of  water  in 
the  apparatus  will  be  at  the  same  level  when  the  pressure 
inside  of  the  apparatus  is  the  same  as  the  atmospheric 
pressure,  and  this  should  be  the  condition  when  the  ex- 
periment is  started.  The  gutta  percha  tube  is  placed  in- 
side the  bottle  containing  the  500  mg.  of  baking  powder 
and  the  apparatus  is  then  connected  up.  Be  sure  the  re- 
lief valve  is  open  when  the  apparatus  is  put  together 
and  closed  immediately  afterwards.  Incline  the  generat- 


BAKING   POWDERS  177 

ing  bottle  to  allow  the  water  to  come  in  contact  with  the 
powder.  Observe  the  evolution  of  gas.  Note  the  height 
of  the  water  column.  Shake  the  generating  bottle  vig- 
orously until  no  more  gas  is  evolved.  Immediately 
afterwards  balance  the  water  columns  by  allowing  some 
water  to  escape  into  the  overflow  flask.  Read  the  fig- 
ure nearest  the  level  of  the  water.  This  reading  indi- 
cates the  per  cent,  of  gas  liberated  by  the  addition  of 
water  to  the  baking  powder,  or  in  other  words,  the  leav- 
ening power  of  the  baking  powder.  This  reading  should 
be  in  the  neighborhood  of  10  per  cent,  in  a  fresh  tartrate 
powder. 


Chapter  XVI 


TEA,  COFFEE,  CHOCOLATE  AND  COCOA 

Tea  consists  of  the  cured,  dried  and  rolled  leaves  of  a 
variety  of  plants  known  as  the  Thea.  According  to  the 
age  of  the  leaf  gathered,  there  are  four  well  known 
grades,  Pekoe  the  youngest,  Souchong  next,  Congou  next 
and  Bohea  the  oldest.  All  these  are  found  in  the  grades 
of  green  or  black  as  the  method  of  curing  varies.  Green 
teas  are  not  fermented,  black  teas  are  fermented,  and 
since  fermentation  tends  to  reduce  the  amount  of  tannin, 
the  latter  are  very  generally  preferred.  The  infusion 
is  made  by  steeping  the  leaves  in  freshly  boiled  water 
(preferably  slightly  hard)  just  below  boiling.  Five 
minutes  is  sufficient  to  make  the  extract,  when  it  will 
contain  the  maximum  of  oil,  extract  and  caffein  and  the 
minimum  of  tannin.  It  should  now  be  poured  off  the 
leaves  and  used.  Boiling  or  long  standing  increases  the 
amount  of  tannin  in  the  infusion,  while  it  does  not 
materially  affect  the  caffein  or  extract. 

Experiments  on  Tea. — Make  an  infusion  according  to 
rule  given  in  the  text,  pour  off  the  clear  liquid,  filtering 
if  necessary,  and  examine  the  leaves  with  a  magnifier. 
Add  a  few  drops  of  the  clear  filtrate  to  a  weak  starch 
solution  faintly  colored  with  iodine;  if  tannin  is  present 


TEA,   COFFEE,    CHOCOLATE  AND   COCOA  179 

the  color  will  fade.  Mix  the  balance  of  the  tea  extract 
with  i/io  of  its  volume  of  chloroform  and  when  settled 
draw  off  the  lower  layer  and  evaporate  in  a  porcelain 
dish  over  hot  water,  the  residue  should  be  almost  color- 
less, crystalline  and  very  bitter  (Caffein). 

Evaporate  some  of  the  tea  extract  after  removing  the 
chloroform  in  a  clean  porcelain  dish  over  hot  water  and 
note  the  large  amount  of  residue,  also  its  color  and 
gummy  nature. 

Coffee  consists  of  the  dried,  fermented  and  roasted 
beans  of  the  caffoea  arabica.  The  extract  is  made  from  the 
finely  pulverized  beans,  which  are  first  mixed  with  cold 
fresh  water  gradually  brought  to  the  boiling-point,  and 
held  there  two  or  three  minutes.  After  settling  of  the 
insoluble  residue,  the  clear  brown  liquid  is  ready  for  use. 
Settling  can  be  hastened  by  the  cautious  addition  of 
cold  water  or  a  coagulating  agent  (white  of  egg). 

Coffee  extract  contains  about  the  same  amount  of 
caffein  and  tannin  as  is  found  in  tea  extract  but  larger 
quantities  of  gum,  dextrine,  etc. 

French  coffee  usually  contains  chicory,  the  kiln  dried 
root  of  the  wild  endive;  the  drying  operation  produces 
caramel  at  the  expense  of  sugar  and  hence  the  water 
extract  is  dark  in  color. 

Coffee  substitutes  are  composed  of  roasted  cereals  or 
breads  with  or  without  the  addition  of  ground  roasted 


l8o  HOUSEHOLD    CHEMISTRY 

coffee.  Their  extracts  may  not  be  entirely  free  from 
caffein  and  tannin,  but  in  any  case  will  contain  less  than 
genuine  coffee.  The  bitter  taste  and  dark  color  are  due 
to  caramel. 

Experiments  on  Coffee. — Grind  the  roasted  beans  to  a 
fine  powder,  throw  half  a  teaspoonful  of  the  powder  into 
a  vessel  holding  cool  water,  stir  well,  and  note  whether 
any  color  is  imparted  to  the  liquid  (chicory). 

Moisten  one  tablespoonful  of  the  powder  with  cold 
water,  add  one  cup  of  warm  water,  bring  to  the  boiling- 
point  and  boil  two  minutes.  Filter  through  paper  or 
cotton  and  reserve  the  clear  filtrate  for  test  as  follows: 

Decolorize  a  small  portion  with  bone-black  and  when 
cold  test  for  starch  with  iodine.  It  should  be  absent ;  if 
present  the  sample  contains  cereal  or  bread. 

Test  another  portion  for  tannin  (see  tea).  Determine 
presence  of  caffein  (as  under  tea).  Chill  some  of  the 
clear  filtrate;  should  it  turn  cloudy,  make  further  test 
for  dextrine  with  alcohol. 

Examine  thoroughly  extracted  coffee  grounds  under 
the  microscope. 

Determine  quality  of  ash. 

Chocolate  and  Cocoa. — These  products  are  made  from 
the  fermented  and  dried  seeds  of  the  fruit  of  the  theo- 
bromo  cacao,  which  resembles  the  cucumber.  After  dry- 
ing and  husking,  the  seeds  yield  two  halves  called  "nibs." 

The  nibs  are  ground  to  a  fine  powder  under  hot  rolls 


TEA,   COFFEE,   CHOCOLATE  AND  COCOA  l8l 

which  melts  the  large  quantity  of  fat  (cocoa  butter) 
present  and  produces  a  liquid  mass.  If  this  is  allowed  to 
run  into  shallow  molds  and  cooled  the  product  is  called 
chocolate  or  bitter  chocolate.  Sugar  and  vanilla  extract 
are  often  added  to  the  liquid  before  cooling,  producing 
sweet  or  edible  chocolate. 

If  the  fluid  mass  of  ground  nibs  is  pressed  to  remove 
fat  and  the  remainder  is  cast  in  molds  and  afterward 
ground,  the  product  is  called  soluble  cocoa.  Alkali  in 
small  amount  is  frequently  used  to  make  the  cocoa  more 
soluble. 

Cheap  grades  of  cocoa  contain  considerable  quantities 
of  starch  and  ground  cocoa  shells. 

Experiments  on  Chocolate  and  Cocoa. — Boil  some  of  the 
finely  ground  mass  with  water,  filter  while  hot  and  re- 
serve both  filtrate  and  residue  for  test. 

Tests  on  Filtrate. — For  starch,  dextrine,  sugar,  protein 
matter  and  soaps. 

Tests  on  Residue. — Dry  and  extract  fatty  matter  with 
gasoline.  Examine  extracted  residue  under  the  micro- 
scope for  fiber.  Determine  quality  and  amount  of  ash. 


Chapter  XVH 

STAINS 

Removal  of  stains  depends  on  the  nature  of  the  fabric, 
quality  of  the  dye  and  character  of  stain. 

/.    Fabrics : 

1.  Silk — most  easily  damaged. 

2.  Wool — next. 

3.  Cotton — next. 

4.  Linen — least. 

II.    Dyes : 

1.  Natural  dyes  least  liable  to  injury. 

2.  Artificial  dyes   (except  indigo  and  alizarine)   most 
susceptible  to  change. 

//.    Solvents : 

1.  Water 

2.  Alcohol. 

3.  Ether. 

4.  Gasoline. 

5.  Chloroform. 

IV.  Absorbents: 

1.  Talc. 

2.  Starch. 

3.  Paper. 


STAINS  183 

V.  Detergents: 

i.  Neutral  soda  or  potash  soaps. 

VI.  Bleaches : 

1.  Peroxide  of  hydrogen. 

2.  Hypochlorites  of  sodium  of  potassium. 

3.  Hyposulphite  of  sodium. 

4.  Sulphites  and  SO2. 

VII.  Neutralising  Agents: 

1.  Ammonia. 

2.  Oxalic  acid  or  acid  oxalate  of  potassium. 

3.  Muriatic  acid,  very  dilute  (HC1). 

4.  Acetic  acid. 

Steaming,  used  when  softening  old  stains  or  in  very 
delicate  fabrics. 

VIII.  Removal  of  stains  and  spots,  co-used  by: 

1.  Fatty  bodies  as  grease  or  oil. 
Use  (a)  Soap  and  water. 

(6)  Ammonia  and  water. 

(c)  Talc. 

(d)  Dry  starch. 

(e)  Paper. 
(/)  Ether. 
(#)  Gasoline. 

2.  Fruits. 
Coloring  matter, 
(a)  Hot  water. 


184  HOUSEHOLD    CHEMISTRY 

(b)  Bleaches — salts  of  lemon  (binoxalate  of  potash). 

Acids. 

Use  dilute  ammonia. 

NOTE: — Do  not  put  ether  or  gasoline  on  a  wet  fabric. 
As  gasoline  and  other  fatty  solvents  tend  to  spread  grease 
spots,  it  is  well  to  mix  them  with  talc  or  starch  and 
apply  to  the  spot.  When  dry,  brush;  repeat  if  necessary. 

3.  Mineral  matter. 
(a)  Rust- 
Use  (i)  Mineral  acids,  HC1,  (on  dyed  fabrics). 

(2)  Organic  acids   (oxalic,  citric  or  tartaric). 

(6)  Acids — 
Use  ammonia. 

4.  Fungoid  growths  as  mildew. 
Use  milk  of  lime  and  a  bleach. 

(a).  Javelle  water. 

(&).  Labarraques  solution. 

(c).  Ammonia  and  peroxide  of  hydrogen. 

(d).  Sunlight. 

(*)•  Milk. 

5.  Ink — Iron  base — 

Use   (i)   Ordinary  ink  not  to  dry,    yields    to    warm 
alcohol. 

(2)  Salts  of  lemon. 

(3)  Oxalic  acid. 


STAINS  185 

6.  Sugar  and  gum — 
Use  warm  water  only. 

7.  Paint  and  varnish — 
If  moist — use  gasoline. 

If  dry — soften  with  amyl  acetate  or  pine  tar  oil  and 
then  remove  with  gasoline. 

8.  Scorch — sunlight. 

9.  Bluing — boil   with   dilute  acid  or  alkali   until   re- 
moved. 


Chapter  XVHI 


Commercial 
forms 


laboratory  strength 


Sp.  gr.    Per  cent.  Concentrated  Sp.  gr.       Dilute  Sp.  gr. 


Vols. 

H20 


Vols. 

acid 


HC1  .........  1.2  40    full  strength     1.2  i          i  i.i 

Vols.       Vols. 

H2O        acid 

HNO3  .......  1.4  70        i  i  1.2  3          i  i.i 

HSSO4  .......  i..°4  94    full  strength     1.84  7          i  i.i 

CHjCOOH...  i.  06  50    full  strength     1.06  10          i  1.007 

Alkalies  ™J     am" 

NH4OH  .....  0.9  28    full  strength      —  i          i  0.945 

NaOH    ......  20  per  cent.        1.3  loper  cent.  1.14 

KOH  .......  —  —     20  per  cent.        1.23  10  per  cent,  i.i 

Salts 

Na2CO3  ......  —  dry  —  loper  cent,  i.i 

BaCl2   .......  —  —  10  per  cent.  — 

(NH*)2C2Oi..  _  saturated 

Na2HPO4  ....  —  _  saturated  — 

NH4C1  .......  —  —  10  per  cent.  — 

(NH4)2SO4.  ••  —  dry  —  saturated 

NaCl  ........  —  dry  saturated  1.2 

MgSO4  ......  —  dry  —  saturated  — 

HgClj  .......  —  —  saturated  — 

Tannin  ......  —  —  20  per  cent.  — 

AgNOs  ......  —  —        5  per  cent.  — 

Co(NO3)2  ----  —  10  per  cent.  — 

K4Fe(CN)6   ..  —  —  10  per  cent.  — 


REAGENTS  187 

SPECIAL  REAGENTS 

Ammonium  Molybdate,  (NH4)2MoO4. 

Dissolve  100  grams  MoO3  in  200  cc.  strong  NH4OH 
and  200  cc.  H2O;  slowly  pour  resulting  solution  in  1500 
cc.  HNO3  sp.  gr.  1.2. 

Magnesia  Mixture. 

i  gram  MgSO4,  i  gram  NH4C1,  4  cc.  ammonia,  8  cc. 
water. 

Millon's  Reagent. — 100  grams  mercury  dissolved  in 
71.5  cc.  HNO3  sp.  gr.  1.4  in  the  cold,  when  action  ceases 
add  twice  the  volume  of  cold  water. 

Fehling's  Reagent. — Solution  A — 34.64  grams  CuSO4, 
5H2O  in  400  cc.  of  cold  water,  when  dissolved  make  up 
to  500  cc. 

Solution  B— 50  grams  NaOH  +180  grams  NaKC4H4O6 
in  300  cc.  of  water,  when  dissolved  and  cooled  make  up  to 
500  cc. 

For  use  mix  equal  volumes  of  A  and  B  and  add  two 
volumes  of  water. 

Barfoed's  Reagent. — 4.0  grams  copper  acetate,  100  cc. 
water,  2  cc.  acetic  acid. 

Nylander's  Reagent. — Two  grams  bismuth  sub-nitrate, 
(BiONO3),  and  4  grams  of  Rochelle  salt,  (NaKC4H4O6), 
in  100  cc.  of  8  per  cent.  NaOH,  sp.  gr.  1.08. 

Nessler's  Reagent. — Dissolve  2  grams  Kl  in  5  cc.  H2O, 
add  4  grams  HgCl2  solution,  or  so  much  that  on  warm- 


l88  HOUSEHOLD    CHEMISTRY 

ing  a  little  of  the  ppt.  remains  undissolved.  After  cool- 
ing, dilute  with  20  cc.  H2O,  filter  and  add  30  cc.  of  a  so- 
lution of  i  gram  of  KOH  in  2  cc.  H2O. 

Soap  Solution  (Stock}. — Dissolve  10  grams  of  good 
castile  soap  in  1,000  cc.  of  90  per  cent,  alcohol. 

For  use  mix  100  cc.  of  the  above  with  100  cc.  of  dis- 
tilled H2O  and  30  cc.  of  alcohol. 

Cries' s  Reagent  for  Nitrites. — Dissolve  i  gram  of  sul- 
phanilic  acid  in  300  cc.  of  acetic  acid  sp.  gr.  1.04  (30  per 
cent). 

Boil  0.2  gram  of  a-naphthylamine  in  400  cc.  of  distilled 
water,  filter  through  a  plug  of  washed  absorbent  cotton 
and  add  360  cc.  of  acetic  acid  (30  per  cent.). 

To  dilute  50  per  cent,  acid  to  30  per  cent.,  take  3/5 
of  loo  or  60  cc.  of  acid  and  dilute  to  100  cc. 

Basic  Acetate  (Sugar  of)  Lead  Solution. — Boil  232 
grams  of  lead  acetate  and  132  grams  of  litharge,  (PbO), 
in  750  cc.  of  distilled  water  for  half  an  hour,  cool  dilute 
to  one  liter.  Allow  liquid  to  stand  until  clear  and  decant. 
Sp.  gr.  of  solution  should  be  about  1.267. 

Alumina  Cream  for  Clarifying  Syrups,  Etc. — Pre- 
cipitate a  solution  of  alum  with  slight  excess  of  ammonia, 
wash  by  decantation  or  filtration  until  neutral  and  sus- 
pend in  water  to  a  creamy  consistency. 

Met  a  Phosphoric  Acid. — Dissolve  glacial  phosphoric 
acid,  (HPO3),  or  phosphoric  anhydride  P2O5  in  ice  and 


REAGENTS  189 

water.    As  the  solution  rapidly  changes  to  H3PO4  make 
it  fresh  for  each  day's  work. 

Alcohol. — 95  per  cent,  is  always  acid,  neutralize  with 
dilute  alkali  before  using.  Alcohol  may  readily  be  re- 
covered from  solutions  and  wash  liquids  by  distilling 
over  hot  water  at  78°-8o°  C. 


List  of  Apparatus  for  Students  in 
Household  Chemistry 


Three  rings   (iron). 
Filter  ring. 
Clamps. 
Triangular  file. 
Round  file. 
Triangles. 
Wire  gauze. 
Steel  forceps. 
Wing-top. 
Horn  spatula. 
Tube   brushes — three    (as- 
sorted sizes). 
Filter-paper. 
Test-tube  holder. 
Scissors. 
Knife. 
Thermometer,     Centigrade 

0°-I20°. 

Glass    rod    with    platinum 

wire. 

Flat  glasses,  4  inch. 
Blue  glass. 

Watch-crystals — four. 
Microscope      slides      with 

cover  glasses — four. 


Test-tubes — i  doz.  6-inch. 
Test-tubes — I  doz.  4-inch. 
Hard  glass  test-tubes  ( I  in. 

X  6  in.) — two. 
Graduate,  10  cc. 
Porcelain     dishes  —   two 

(3l/2  inch). 
Beakers  (Jaikel  1-4). 
Tripod. 

Test-tube  rack. 
Agate   boilers   with   cover, 

l/2  pint. 
2    funnels — two    inch   and 

three  inch. 

Flasks — one  4  oz.  high. 
Flasks — two     4     oz.     low 

(wide  mouth). 
Flask — one   16    oz.    round 

bottom. 

Wash-bottle — 16  oz. 
Wide  mouth  bottle,  8  oz. 
Water-bath,  5  in. 


School  of  Household  Arts 


Teachers  College,  Columbia  University 


Two  years  curricula  leading  to 
Diploma  and  Bachelor's  Degree; 
Teaching  and  Supervision  of 
Domestic  cArt,  Domestic  Science 
and  Hospital  Economy. 

Professional  Courses  in  Institu- 
tional ^Administration,  Dietetics 
and  House  Decorations. 

Also  graduate  stud/"  leading  to 
the  A.M.  and  Ph.D.  Diplomas 
and  Degrees. 


Detailed  information  on  application 
to   Secretary   of   Teachers    College 


All  the  Apparatus  and  Chemicals  mentioned 
in  this  book  are  kept  in  stock  by 

EIMER   &  AMEND 

Laboratory  Furnishers 

205-211  Third  Avenue,  corner  Eighteenth  Street 
NEW  YORK  CITY 


Headquarters  for—- 
Chemical Apparatus 
Pure  Chemicals  for  Household  Use 
Hydrometers 
Oven  Thermometers 
Balances  and  Weights 
Nickel  and  Platinum  Ware 


Every~  Domestic  Science  Laboratory 
should  be  equipped  with 

Standard  Measuring  Spoons 

Consisting  of  separate  tea  and  tablespoons 
and  leveler.  Made  in  heavy  white  metal. 
Cleans  and  looks  like  silver.  Price, 
seventy-five  cents  per  set,  postage  free  to 
any  part  of  the  United  States  or  Canada. 
Prices  for  large  lots  on  application  to 

H.  T.  VULTE 

33  Park  Ave.,  New  RocHelle,  N.  Y. 


Hermann  T.  Vulte,  Ph.D.,  F.C.S. 

Chemical  and  Sanitary 
Engineer 

Analyses  and  opinions  of  Food  Products, 
Detergents,  Textiles,  Fuels,  Etc. 

33  PARK  AVE.,    -     NEW  ROCHELLE,  N.Y. 


^       UWi^VV^WUV^WU»>VOUWUi>OW<>i>wOw^OK>Wi>^*A>WWi>C 

F.  W.  DEVOE  & 
i    C.  T.  RAYNOLDS  CO. 


( i 

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<  I  Makers  of 

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c  i 

(  i 

( I 
( I 

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Dry  Colors,  Paints, 

i  S 

Varnishes,  Brushes 

and 
Artists'    Materials 


101  FULTON  STREET, 
NEW  YORK 


Founded  1754 


This  book  is  DUE  on  the  last  date  stamped  below 


Form  L-9-10n»-5,'28 


=9 

ilte  - 


.ahnratnry  notes  in 
Behold  chemist 


TX 


V3U 


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